- Email: [email protected]
Self-powered, broadband perovskite photodetector based on ZnO microspheres as scaffold layer
Applied Surface Science 448 (2018) 23–29
Contents lists available at ScienceDirect
Applied Surface Science journal homepage: www.elsevier.com/locate/apsusc
Short Communication
Self-powered, broadband perovskite photodetector based on ZnO microspheres as scaffold layer Yifan Zhu 1, Zehao Song 1, Hai Zhou ⇑, Dingjun Wu, Runhao Lu, Rui Wang, Hao Wang ⇑ Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials, Hubei Key Laboratory of Ferro & Piezoelectric Materials and Devices, Faculty of Physics & Electronic Science, Hubei University, Wuhan 430062, PR China
a r t i c l e
i n f o
Article history: Received 22 February 2018 Revised 3 April 2018 Accepted 5 April 2018 Available online 10 April 2018 Keywords: ZnO microsphere Photodetector Self-powered Perovskite
a b s t r a c t A self-powered CH3NH3PbI3 photodetector (PD) based on ZnO microsphere (MS) array scaffold was reported. Through scanning electron microscopy images, a ZnO microsphere array consisted of nanosheets can be seen on ZnO mesh structure. Based on this novel structure, we first fabricated CH3NH3PbI3 photodetector with ZnO MS as the electron selective layer and MoO3 hole selective layer. Under light, the PDs showed the detection wavelength ranges from 300 to 800 nm, the responsivity values up to 48 mA/W, detectivity values as large as 4.5 1011 Jones, on/off ratio up to 1400, and rise and fall time less than 14 ms, these results are comparable with the reported perovskite PDs. Furthermore, because of the effective absorption for ZnO microsphere in ultraviolet (UV) region, our device showed a significant UV detection performance. These results have great value on the scaffolds of perovskite materials for high performance devices. Ó 2018 Elsevier B.V. All rights reserved.
1. Introduction Organic-inorganic hybrid lead halide perovskite materials are extraordinarily promising for applications in fabrication of highperformance photovoltaic solar cells [1–4], light-emitting diodes (LEDs) [5], photodetectors (PDs) [6,7], and lasers [8], resulting from their ultrafast charge generation, high absorption coefficient and relatively large mobility. CH3NH3PbX3 (MAPbX3, X = Cl, Br, I), with a direct and tunable band gap, is very valuable as photosensitive materials for PDs to obtain broader response spectra ranging from near ultraviolet to whole visible light [9–16]. Perovskite PD based on (FASnI3)0.6(MAPbI3)0.4 as active layers was demonstrated to have the wavelength ranging from 300 to 1000 nm with dark current of 3.9 nA, responsivity (R) of over 0.4 A W1 and specific detectivity of over 1012 Jones in the near-infrared region under 0.2 V [17]. Sutherland et al. showed a perovskite diode photodetector based on TiO2/perovskite/spiro-OMeTAD with the response wavelength ranging from 400 to 780 nm and this device has a peak self-powered responsivity of 0.4 A/W at 600 nm [18]. In recent years, aligned nanostructures, taking the forms of nanowires [19–21], nanorods (NRs) [22–24] or nanotubes [25,26], have attracted much attention as scaffolds in highly effi-
⇑ Corresponding authors. 1
E-mail addresses: [email protected] (H. Zhou), [email protected] (H. Wang). These authors contributed equally to this work.
https://doi.org/10.1016/j.apsusc.2018.04.047 0169-4332/Ó 2018 Elsevier B.V. All rights reserved.
cient perovskite solar cells and PDs due to their large surface-tovolume ratio and direct conduction path for electrons. The perovskite solar cells based on TiO2 nanorod arrays scaffold with 4.8 nm atomic-layer-deposited passivated layer exhibited a power conversion efficiency of 13.45% with the short-circuit current density (Jsc) =19.78 mA/cm2, the open-circuit voltage (VOC) = 0.945 V, and fill factor (FF) = 0.72 [27]. Norah Alwadai and co-authors reported a vertically injected broadband UV-to-IR photodetector based on Gd-doped ZnO NRs/CH3NH3PbI3 perovskite heterojunction with a high photoresponsivity of 28 and 0.22 A/W, for white light and IR illumination, respectively, with high detectivity values of 1.1 1012 and 9.3 109 Jones [28]. Despite exciting progress, these devices based on aligned nanostructure scaffold suffer from limited performance due to small gap between aligned nanostructures and large length of the nanostructure, which blocks the penetration of perovskite into nano-arrays and inhibit the carrier transport, respectively. Herein, we report a microsphere array as perovskite scaffold layer, below which is a mesh structure for the transport of carrier. The PDs use ZnO MS as the electron selective layer (ESL), MoO3 hole selective layer (HSL) and a device configuration of glass/ FTO/ZnO MS/MAPbI3/ MoO3/Au. Under light, the PDs showed the detection wavelength ranges from 300 to 800 nm, the responsivity values up to 48 mA/W, detectivity values as large as 4.5 1011 Jones, on/off ratio up to 1400, and rise and fall time bellow 14
24
Y. Zhu et al. / Applied Surface Science 448 (2018) 23–29
ms. These performances are comparable with the reported perovskite PDs.
by annealing at 70 °C for 5 min. Then the samples were quickly put into MAI solution for 3 min, and rinsed into the IPA, then annealed on hotplate for 5 min.
2. Experiment 2.3. The deposition of the HSL and Au electrode 2.1. Growth of ZnO microspheres FTO glasses were washed by deionised water, acetone, and ethanol for 20 min, respectively. Then the cleaned FTO glass was placed at the bottom of the beaker and 50 ml of precursor solution (10 mM/L) with 0.8924 g zinc nitrate hexahydrate, 0.4206 g hexamethylenetetramine and 0.2240 g sodium citrate dihydrate in 300 ml deionized water was slowly tipped into the beaker, and which was put into a water bath at 90 °C for 2 h. Finally, the samples were rinsed with deionized water and dried in an N2 atmosphere. In order to improve the crystallinity of ZnO microspheres, the samples were annealed at 300 °C for 2 h in the atmospheric environment. In addition, to study the effect of concentration of precursor solution, the diluted solution with four groups such as 5 times (2 mM/L), 6 times (1.67 mM/L), 7 times (1.43 mM/L) and 8 times (1.25 mM/L) was used. 2.2. Preparation of CH3NH3PbI3 halide perovskite layers The perovskite was prepared using the sequential deposition method. First, MAI was dissolved in 2-propanol solvent (IPA) to form 10 mg ml1 solution. A PbI2 solution (dissolved overnight in N,N-dimethylformamide at a concentration of 461 mg ml1) was spin-coated onto the ZnO MS layer at 3000 rpm for 30 s followed
After the MAPbI3 halide perovskite was prepared, 14 nm MoO3 HSL was evaporated on the samples. Then a 60 nm Au electrode was deposited on MoO3 layers using thermal evaporation method at a deposition rate of 0.8 Ǻ/s. Finally we got the device with effective area of 0.07 cm2. 2.4. Characterization The morphology and crystallinity of the samples were characterized by field emission scanning electron microscopy (FESEM, JEOL, JSM-6700F) and X-ray diffraction (XRD, D8 FOCUS X-ray diffraction), respectively. All the current-voltage (I–V) and current-time (I-T) characteristics were measured by an Agilent B1500 electrometer. The photosensitivity was measured using a photoelectric detector spectral response measurement system (DSR100, from Beijing Saifan Optoelectronics Co., Ltd.). The sample was under direct illumination, and the optical power of light was calibrated by a ultraviolet (UV)-enhanced Si detector. 3. Results and discussion In order to effectively widen the contact area between the scaffold and perovskite, ZnO microsphere needs to be optimized. For
Fig. 1. SEM Image of the ZnO MS with various dilution times of precursors, (a) 5 (2 mM/L), (b) 6 (1.67 mM/L), (c) 7 (1.43 mM/L) and (d) 8 times (1.25 mM/L). (e) The enlarged SEM image of (c). (f) the SEM image of the MAPbI3 on ZnO MS array. (g) The transmission of the ZnO MS film with various dilution times of precursors. (h) Absorption spectrum of MAPbI3/ZnO MS array structure. (i) XRD patterns of MAPbI3/ZnO MS array structure.
Y. Zhu et al. / Applied Surface Science 448 (2018) 23–29
this, the precursors concentration is a key reaction condition to control the morphology of ZnO microspheres and the SEM images of ZnO microspheres with various precursors concentration are shown in Fig. 1a–d. Through diluting the precursors concentration from 5 to 8 times, the ZnO microspheres will decrease dramatically. Also the ZnO microsphere was consist of many nanosheets, bellow which ZnO nano-mesh structure can be seen (Fig. 1e). Based on our knowledge, much of ZnO microspheres stacked will result in big series resistance and block the carrier transport. In contrast, the sample with little ZnO microspheres will be filled by few perovskite particles, which will generate little photocurrent. So the perfect perovskite scaffold should be a monolayer and uniformly distributed ZnO microspheres on ZnO mesh nanosheet, which
25
would effectively utilize the ultrahigh surface areas of the ZnO microspheres and decrease the series resistance of devices. Thus, the solution with the six-time dilution of precursor solution may be the best. Above ZnO microspheres, the MAPbI3 perovskite layer was seen clearly with the grain size of 500–700 nm (Fig. 1f). And the ZnO microspheres were surrounded by perovskite and some perovskite grains penetrate between the nanospheres successfully, showing good contact between ZnO microspheres and perovskite. In addition, an over 80% transmittance of the ZnO microsphere film prepared with various dilution precursor solution in visible region is obtained as shown in Fig. 1(g), indicating most visible light can be absorbed by perovskite. Fig. 1 h shows the absorption spectra of the ZnO MSs /MAPbI3 ranging from 300 to 800 nm. The
Fig. 2. (a) Schematic illustration of the perovskite PD. (b) The schematic band diagram of the device. The I-V curve of the device with various dilution times of precursors, (c) 5 (2 mM/L), (d) 6 (1.67 mM/L), (e) 7 (1.43 mM/L) and (f) 8 times (1.25 mM/L).
26
Y. Zhu et al. / Applied Surface Science 448 (2018) 23–29
Fig. 3. (a) I-T curves of the device with various dilution times under UV light with the light intensity of 2 mW/cm2. (b) On/off ratio image of the device with various dilution times under UV light with the light intensity of 2 mW/cm2. Wavelength-dependent R (c) and Dk (d) at 0 V. (e) I-V curves of the devices prepared by 1.67 mM/L solution under various monochromatic light with light intensity of 1.6 mW/cm2.
absorption spectrum of the MAPbI3 on ZnO shows a strong absorption from the near-IR region to 300 nm, which may result in a wide response in this region for a broadband photodetector. The XRD patterns revealed in Fig. 1i match well with a tetragonal perovskite structure with little addition of PbI2 whose affraction peak located
at 12.70°, the moderate residual of PbI2 could deliver stable and high performance of device [29]. Structure diagram of ZnO MSs/MAPbI3/MoO3 photodetector was illustrated in Fig. 2a and b shows the schematic band diagram of the device. When the device is irradiated by light, perovskite
Table 1 The performance parameters of perovskite-based PDs in this and previously reported work.
*
Structure
On/off ratio
Responsivity (mA/W)
Detectivity (1011 Jones)
Rise time (s)
Delay time (s)
On/off ratio
Device 1* Device 2* Device 3* Device 4* ITO/ CH3NH3PbI3/ITO ZnO/CsPbBr3 CH3NH3PbBr3 nanowire TiO2/CH3NH3PbBr3
150 1400 362 255 173 12.86 61.9 <10
29 48 12 17 160 11.5 – 11.5
1.8 4.5 3.2 1.9 – – – –
– 0.014 – – 2.2 0.409 0.12 2.3
– 0.012 – – 0.3 0.0179 0.086 2.76
This This This This 32 33 34 35
Device 1, 2, 3 and 4 is the device with diluting precursor solution for 5 (2 mM/L), 6 (1.67 mM/L), 7 (1.43 mM/L) and 8 times (1.25 mM/L), respectively.
work work work work
Y. Zhu et al. / Applied Surface Science 448 (2018) 23–29
film will absorb photons and generate carrier (when the photons energy is larger than the band gap of semiconductor), and photogenerated electron-hole pairs will be by ESL and HSL, generating photocurrent, which is the principle of the self-powered device. Fig. 2c–f are the I-V curves of the device with various dilution times of precursors and all devices show good photovoltaic performance. We checked the short current (Isc) of the device, which increases with increasing dilution times and then decrease with high dilution times. The biggest Isc is 6.66 lA for the device prepared by 1.67 mM/L solution. In addition, compared to high-fold dilution, the device with low-fold dilution solution shows more smooth IV curves, showing that more ZnO MSs will benefit the interface contact between ZnO and perovskite. We next study the time response properties of the device with various dilution at zero bias. The I-T curves (Fig. 3a) show that all devices have good photoresponse with fast rise and fall speed. Similar to above, the device prepared by 1.67 mM/L solution shows best photoresponse characteristic. Based on this I-T curves, the on/off ratio is extracted and shown in Fig. 3b. We can see clearly that the device prepared by 1.67 mM/L solution shows biggest on/off ratio with the value as high as 1400, much higher than that of the other devices. The spectral R and detectivity (Dk) are two key parameters to characterize sensitivity of photodetectors [30,31], which are defined by the equations
R¼
J ph Llight
R Dk ¼ pffiffiffiffiffiffiffiffiffiffiffiffiffiffi 2qJdark
ð1Þ
ð2Þ
27
where Jph is the photocurrent density of the photodetectors, Llight is the applied optical power density, q is electron charge, and Jdark is dark current density, respectively. Seen from Fig. 3c and d, all of the photodetectors have a wide response spectrum ranging from 300 to 800 nm which due to the absorption characteristics of ZnO and MAPbI3 perovskite. However, the responsivity and detectivity of the device prepared by 1.67 mM/L solution, measured without applied voltages, are higher than those of the other devices. In addition, the responsivity and detectivity show a increase trend with decreasing the wavelength and reach a biggest value of 48 mA/W at around 380 nm, which may be attributed to ZnO. Furthermore, at the whole response wavelength the detectivity of the device prepared by 1.67 mM/L solution is above 1011 Jones (1 Jone = 1 cm Hz/W) and the biggest value is about 4.5 1011 Jones at around 380 nm. These results are comparable with the previous work [13,32–34] and the detailed comparison is shown in Table 1. Note that because of the effective absorption for ZnO microsphere in UV region, our device showed a significant UV detection performance. Fig. 3e is the I-V curves of the devices prepared by 1.67 mM/L solution under various monochromatic light with light intensity of 1.6 mW/cm2, showing our devices have a wide response spectrum ranging from 300 to 800 nm, which is consistent with the responsivity curves. From above, the device prepared by 1.67 mM/L solution displays best performance and here the detailed other performance is shown. Under various light intensity, the device shows obviously distinguishable I-V curves (Fig. 4a), displays that the photoresponse is actually dependent on the incident light intensity, which is reasonable in that stronger illumination will generate more photon-excited electron–hole pairs, and therefore leads to higher photocurrent in the circuit. It was also observed that the photocur-
Fig. 4. The performance of the device prepared by 1.67 mM/L solution. (a) I-V curves of the devices at various incident light intensity. (b) The dependence of photocurrent on operating light intensity at 0 V. (c) The dependence of photocurrent on operating time at 0 V. (d) The fast response time test.
28
Y. Zhu et al. / Applied Surface Science 448 (2018) 23–29
rent was highly related to bias voltage. We further checked the photocurrent of the detector at zero bias (Fig. 4b), which increases linearly with increasing light intensity and then reaches saturation with high light intensity (>2.5 mW/cm2). The saturated photocurrent demonstrates that the absorption capacity of the material reaches the limitation. Furthermore, the dependence of photocurrent on operating time at 0 V for the device is shown in Fig. 4c, which illustrates the device has good stability under illumination and fast time response characteristic. When the light is on, the photocurrent changes very clearly and ranges from nA to lA level. In addition, under illumination for about 800 s, the photocurrent has no attenuation and after that it can also exhibit well on/off photo switching behavior. Its detailed time response is illustrated in Fig. 4d and it can be seen that the value of rise and delay time is about 14 and 12 ms, respectively. Our device showed very good performance, we think the main reason is attributed to the ZnO MS scaffold. In the ZnO MS scaffold, many ZnO MSs are composed of nanosheets, which will beneficial for the cover of perovskite on ZnO, obtain more contact interfaces between ZnO and perovskite. Under light, much of photons absorbed by perovskite will generate many photogenerated carriers, which will be separated easily due to the increased interface. In addition, under the ZnO MSs there is ZnO mesh structure, which will block the perovskite to contact with FTO directly and can facilitate the transport of carrier. So our novel ZnO MS structure is very crucial for the good performance of the perovskite PDs. 4. Conclusion In summary, a self-powered CH3NH3PbI3 PD based on ZnO MS array scaffold was reported. Through SEM images, a ZnO microsphere array constituted by many nanosheets can be seen on ZnO mesh structure. Based on this novel structure, we first fabricated CH3NH3PbI3 photodetector with ZnO MS as the electron selective layer and MoO3 hole selective layer. Under light, the PDs showed the detection wavelength ranges from 300 to 800 nm, the responsivity values up to of 48 mA/W, detectivity values as large as 4.5 1011 Jones, on/off ratio up to 1400, and rise and fall time bellow 14 ms. These performances are comparable with the reported perovskite PDs. Acknowledgements This work is supported in part by the National Natural Science Foundation of China (No. 51372075). References [1] M. Saliba, T. Matsui, K. Domanski, J.Y. Seo, A. Ummadisingu, S.M. Zakeeruddin, J.P. Correa-Baena, W.R. Tress, A. Abate, A. Hagfeldt, M. Grätzel, Incorporation of rubidium cations into perovskite solar cells improves photovoltaic performance, Science 354 (6309) (2016) 206–209. [2] N. Arora, M.I. Dar, A. Hinderhofer, N. Pellet, F. Schreiber, S.M. Zakeeruddin, M. Grätzel, Perovskite solar cells with CuSCN hole extraction layers yield stabilized efficiencies greater than 20%, Science 28 (2017) eaam5655. [3] D. Bi, C. Yi, J. Luo, J.D. Décoppet, F. Zhang, S.M. Zakeeruddin, X. Li, A. Hagfeldt, M. Grätzel, Polymer-templated nucleation and crystal growth of perovskite films for solar cells with efficiency greater than 21%, Nat. Energy 1 (2016) 16142. [4] D. Zhao, Y. Yu, C. Wang, W. Liao, N. Shrestha, C.R. Grice, A.J. Cimaroli, L. Guan, R. J. Ellingson, K. Zhu, X. Zhao, Low-bandgap mixed tin–lead iodide perovskite absorbers with long carrier lifetimes for all-perovskite tandem solar cells, Nat. Energy 2 (2017) 17018. [5] L. Meng, E.P. Yao, Z. Hong, H. Chen, P. Sun, Z. Yang, G. Li, Y. Yang, Pure formamidinium-based perovskite light-emitting diodes with high efficiency and low driving voltage, Adv. Mater. 29 (4) (2017) 1603826. [6] J. Feng, X. Yan, Y. Liu, H. Gao, Y. Wu, B. Su, L. Jiang, Crystallographically aligned perovskite structures for high-performance polarization-sensitive photodetectors, Adv. Mater. 29 (16) (2017) 1605993.
[7] H. Zhou, J. Mei, M. Xue, Z. Song, H. Wang, High-stability, self-powered perovskite photodetector based on a CH3NH3PbI3/GaN heterojunction with C60 as an electron transport layer, J. Phys. Chem. C 121 (39) (2017) 21541– 21545. [8] P. Liu, X. He, J. Ren, Q. Liao, J. Yao, H. Fu, Organic-inorganic hybrid perovskite nanowire laser arrays, ACS Nano 11 (6) (2017) 5766–5773. [9] L. Dou, Y.M. Yang, J. You, Z. Hong, W.H. Chang, G. Li, Y. Yang, Solutionprocessed hybrid perovskite photodetectors with high detectivity, Nature Commun. 5 (2014) 5404. [10] S. Tong, J. Sun, C. Wang, Y. Huang, C. Zhang, J. Shen, H. Xie, D. Niu, S. Xiao, Y. Yuan, J. He, High-performance broadband perovskite photodetectors based on CH3NH3PbI3/C8BTBT heterojunction, Adv. Electron. Mater. 3 (7) (2017) 1700058. [11] S. Tong, H. Wu, C. Zhang, S. Li, C. Wang, J. Shen, S. Xiao, J. He, J. Yang, J. Sun, Y. Gao, Large-area and high-performance CH3NH3PbI3 perovskite photodetectors fabricated via doctor blading in ambient condition, Org. Electron. 49 (2017) 347–354. [12] S. Li, S. Tong, J. Yang, H. Xia, C. Zhang, C. Zhang, J. Shen, S. Xiao, J. He, Y. Gao, B. Yang, High-performance formamidinium-based perovskite photodetectors fabricated via doctor-blading deposition in ambient condition, Org. Electron. 47 (2017) 102–107. [13] H. Lu, W. Tian, F. Cao, Y. Ma, B. Gu, L. Li, A self-powered and stable allperovskite photodetector-solar cell nanosystem, Adv. Funct. Mater. 26 (8) (2016) 1296–1302. [14] L. Shen, Y. Fang, D. Wang, Y. Bai, Y. Deng, M. Wang, Y. Lu, J. Huang, A selfpowered, sub-nanosecond-response solution-processed hybrid perovskite photodetector for time-resolved photoluminescence-lifetime detection, Adv. Mater. 28 (48) (2016) 10794–10800. [15] M.I. Saidaminov, M.A. Haque, J. Almutlaq, S. Sarmah, X.H. Miao, R. Begum, A.A. Zhumekenov, I. Dursun, N. Cho, B. Murali, O.F. Mohammed, Inorganic lead halide perovskite single crystals: phase-selective low-temperature growth, carrier transport properties, and self-powered photodetection, Adv. Opt. Mater. 5 (2) (2017) 1600704. [16] H. Fang, Q. Li, J. Ding, N. Li, H. Tian, L. Zhang, T. Ren, J. Dai, L. Wang, Q. Yan, A self-powered organolead halide perovskite single crystal photodetector driven by a DVD-based triboelectric nanogenerator, J. Mater. Chem. C 4 (3) (2016) 630–636. [17] W. Wang, D. Zhao, F. Zhang, L. Li, M. Du, C. Wang, Y. Yu, Q. Huang, M. Zhang, L. Li, J. Miao, Highly sensitive low-bandgap perovskite photodetectors with response from ultraviolet to the near-infrared region, Adv. Funct. Mater. 27 (42) (2017). [18] B.R. Sutherland, A.K. Johnston, A.H. Ip, J. Xu, V. Adinolfi, P. Kanjanaboos, E.H. Sargent, Sensitive, fast, and stable perovskite photodetectors exploiting interface engineering, Acs Photonics 2 (8) (2015) 1117–1123. [19] J. Qiu, Y. Qiu, K. Yan, M. Zhong, C. Mu, H. Yan, S. Yang, All-solid-state hybrid solar cells based on a new organometal halide perovskite sensitizer and onedimensional TiO2 nanowire arrays, Nanoscale 5 (8) (2013) 3245–3248. [20] Y. Sanehira, Y. Numata, M. Ikegami, T. Miyasaka, Photovoltaic properties of two-dimensional (CH3(CH2)3NH3)2PbI4 perovskite crystals oriented with TiO2 nanowire array, Chem. Lett. 46 (2017) 1204. [21] J. Huang, M. Wang, L. Ding, F. Igbari, X. Yao, Efficiency enhancement of MAPbIxCl 3 x based perovskite solar cell by modifying the TiO2 interface with silver nanowires, Sol. Energy 130 (2016) 273–280. [22] S.S. Mali, C.S. Shim, H.K. Park, J. Heo, P.S. Patil, C.K. Hong, Ultrathin atomic layer deposited TiO2 for surface passivation of hydrothermally grown 1D TiO2 nanorod arrays for efficient solid-state perovskite solar cells, Chem. Mater. 27 (5) (2015) 1541–1551. [23] H. Zhou, Z. Song, P. Tao, H. Lei, P. Gui, J. Mei, H. Wang, G. Fang, Self-powered, ultraviolet-visible perovskite photodetector based on TiO2 nanorods, RSC Adv. 6 (8) (2016) 6205–6208. [24] M.S. Seo, I. Jeong, J.S. Park, J. Lee, I.K. Han, W.I. Lee, H.J. Son, B.H. Sohn, M.J. Ko, Vertically aligned nanostructured TiO2 photoelectrodes for high efficiency perovskite solar cells via a block copolymer template approach, Nanoscale 8 (22) (2016) 11472–11479. [25] M. Krbal, H. Sopha, V. Podzemna, S. Das, J. Prikryl, J.M. Macak, TiO2 nanotube/ chalcogenide-based photoelectrochemical cell: nanotube diameter dependence study, J. Phys. Chem. C 121 (11) (2017) 6065–6071. [26] X. Wang, S.A. Kulkarni, Z. Li, W. Xu, S.K. Batabyal, S. Zhang, A. Cao, L.H. Wong, Wire-shaped perovskite solar cell based on TiO2 nanotubes, Nanotechnology 27 (20) (2016) 20LT01. [27] H.S. Kim, J.W. Lee, N. Yantara, P.P. Boix, S.A. Kulkarni, S. Mhaisalkar, M. Grätzel, N.G. Park, High efficiency solid-state sensitized solar cell-based on submicrometer rutile TiO2 nanorod and CH3NH3PbI3 perovskite sensitizer, Nano Lett. 13 (6) (2013) 2412–2417. [28] N. Alwadai, M.A. Haque, S. Mitra, T. Flemban, Y. Pak, T. Wu, I. Roqan, Highperformance ultraviolet-to-infrared broadband perovskite photodetectors achieved via inter-/intraband transitions, ACS Appl. Mater. Interfaces 9 (43) (2017) 37832–37838. [29] Q. Jiang, Z. Chu, P. Wang, X. Yang, H. Liu, Y. Wang, Z. Yin, J. Wu, X. Zhang, J. You, Planar-structure perovskite solar cells with efficiency beyond 21%, Adv. Mater. 29 (46) (2017) 1703852. [30] H. Zhou, P. Gui, Q. Yu, J. Mei, H. Wang, G. Fang, Self-powered, visible-blind ultraviolet photodetector based on n-ZnO nanorods/i-MgO/p-GaN structure light-emitting diodes, J. Mater. Chem. C 3 (5) (2015) 990–994.
Y. Zhu et al. / Applied Surface Science 448 (2018) 23–29 [31] L. Yang, H. Zhou, M. Xue, Z. Song, H. Wang, A self-powered, visible-blind ultraviolet photodetector based on n-Ga: ZnO nanorods/p-GaN heterojunction, Sens. Actuators, A 267 (2017) 76–81. [32] C. Li, C. Han, Y. Zhang, Z. Zang, M. Wang, X. Tang, J. Du, Enhanced photoresponse of self-powered perovskite photodetector based on ZnO nanoparticles decorated CsPbBr 3 films, Sol. Energy Mater. Sol. Cells 172 (2017) 341–346.
29
[33] S. Zhuo, J. Zhang, Y. Shi, Y. Huang, B. Zhang, Self-template-directed synthesis of porous perovskite nanowires at room temperature for high-performance visible-light photodetectors, Angew. Chemie Int. Ed. 54 (19) (2015) 5693– 5696. [34] M. Cao, J. Tian, Z. Cai, L. Peng, L. Yang, D. Wei, Perovskite heterojunction based on CH3NH3PbBr 3 single crystal for high-sensitive self-powered photodetector, Appl. Phys. Lett. 109 (23) (2016) 233303.
Contents lists available at ScienceDirect
Applied Surface Science journal homepage: www.elsevier.com/locate/apsusc
Short Communication
Self-powered, broadband perovskite photodetector based on ZnO microspheres as scaffold layer Yifan Zhu 1, Zehao Song 1, Hai Zhou ⇑, Dingjun Wu, Runhao Lu, Rui Wang, Hao Wang ⇑ Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials, Hubei Key Laboratory of Ferro & Piezoelectric Materials and Devices, Faculty of Physics & Electronic Science, Hubei University, Wuhan 430062, PR China
a r t i c l e
i n f o
Article history: Received 22 February 2018 Revised 3 April 2018 Accepted 5 April 2018 Available online 10 April 2018 Keywords: ZnO microsphere Photodetector Self-powered Perovskite
a b s t r a c t A self-powered CH3NH3PbI3 photodetector (PD) based on ZnO microsphere (MS) array scaffold was reported. Through scanning electron microscopy images, a ZnO microsphere array consisted of nanosheets can be seen on ZnO mesh structure. Based on this novel structure, we first fabricated CH3NH3PbI3 photodetector with ZnO MS as the electron selective layer and MoO3 hole selective layer. Under light, the PDs showed the detection wavelength ranges from 300 to 800 nm, the responsivity values up to 48 mA/W, detectivity values as large as 4.5 1011 Jones, on/off ratio up to 1400, and rise and fall time less than 14 ms, these results are comparable with the reported perovskite PDs. Furthermore, because of the effective absorption for ZnO microsphere in ultraviolet (UV) region, our device showed a significant UV detection performance. These results have great value on the scaffolds of perovskite materials for high performance devices. Ó 2018 Elsevier B.V. All rights reserved.
1. Introduction Organic-inorganic hybrid lead halide perovskite materials are extraordinarily promising for applications in fabrication of highperformance photovoltaic solar cells [1–4], light-emitting diodes (LEDs) [5], photodetectors (PDs) [6,7], and lasers [8], resulting from their ultrafast charge generation, high absorption coefficient and relatively large mobility. CH3NH3PbX3 (MAPbX3, X = Cl, Br, I), with a direct and tunable band gap, is very valuable as photosensitive materials for PDs to obtain broader response spectra ranging from near ultraviolet to whole visible light [9–16]. Perovskite PD based on (FASnI3)0.6(MAPbI3)0.4 as active layers was demonstrated to have the wavelength ranging from 300 to 1000 nm with dark current of 3.9 nA, responsivity (R) of over 0.4 A W1 and specific detectivity of over 1012 Jones in the near-infrared region under 0.2 V [17]. Sutherland et al. showed a perovskite diode photodetector based on TiO2/perovskite/spiro-OMeTAD with the response wavelength ranging from 400 to 780 nm and this device has a peak self-powered responsivity of 0.4 A/W at 600 nm [18]. In recent years, aligned nanostructures, taking the forms of nanowires [19–21], nanorods (NRs) [22–24] or nanotubes [25,26], have attracted much attention as scaffolds in highly effi-
⇑ Corresponding authors. 1
E-mail addresses: [email protected] (H. Zhou), [email protected] (H. Wang). These authors contributed equally to this work.
https://doi.org/10.1016/j.apsusc.2018.04.047 0169-4332/Ó 2018 Elsevier B.V. All rights reserved.
cient perovskite solar cells and PDs due to their large surface-tovolume ratio and direct conduction path for electrons. The perovskite solar cells based on TiO2 nanorod arrays scaffold with 4.8 nm atomic-layer-deposited passivated layer exhibited a power conversion efficiency of 13.45% with the short-circuit current density (Jsc) =19.78 mA/cm2, the open-circuit voltage (VOC) = 0.945 V, and fill factor (FF) = 0.72 [27]. Norah Alwadai and co-authors reported a vertically injected broadband UV-to-IR photodetector based on Gd-doped ZnO NRs/CH3NH3PbI3 perovskite heterojunction with a high photoresponsivity of 28 and 0.22 A/W, for white light and IR illumination, respectively, with high detectivity values of 1.1 1012 and 9.3 109 Jones [28]. Despite exciting progress, these devices based on aligned nanostructure scaffold suffer from limited performance due to small gap between aligned nanostructures and large length of the nanostructure, which blocks the penetration of perovskite into nano-arrays and inhibit the carrier transport, respectively. Herein, we report a microsphere array as perovskite scaffold layer, below which is a mesh structure for the transport of carrier. The PDs use ZnO MS as the electron selective layer (ESL), MoO3 hole selective layer (HSL) and a device configuration of glass/ FTO/ZnO MS/MAPbI3/ MoO3/Au. Under light, the PDs showed the detection wavelength ranges from 300 to 800 nm, the responsivity values up to 48 mA/W, detectivity values as large as 4.5 1011 Jones, on/off ratio up to 1400, and rise and fall time bellow 14
24
Y. Zhu et al. / Applied Surface Science 448 (2018) 23–29
ms. These performances are comparable with the reported perovskite PDs.
by annealing at 70 °C for 5 min. Then the samples were quickly put into MAI solution for 3 min, and rinsed into the IPA, then annealed on hotplate for 5 min.
2. Experiment 2.3. The deposition of the HSL and Au electrode 2.1. Growth of ZnO microspheres FTO glasses were washed by deionised water, acetone, and ethanol for 20 min, respectively. Then the cleaned FTO glass was placed at the bottom of the beaker and 50 ml of precursor solution (10 mM/L) with 0.8924 g zinc nitrate hexahydrate, 0.4206 g hexamethylenetetramine and 0.2240 g sodium citrate dihydrate in 300 ml deionized water was slowly tipped into the beaker, and which was put into a water bath at 90 °C for 2 h. Finally, the samples were rinsed with deionized water and dried in an N2 atmosphere. In order to improve the crystallinity of ZnO microspheres, the samples were annealed at 300 °C for 2 h in the atmospheric environment. In addition, to study the effect of concentration of precursor solution, the diluted solution with four groups such as 5 times (2 mM/L), 6 times (1.67 mM/L), 7 times (1.43 mM/L) and 8 times (1.25 mM/L) was used. 2.2. Preparation of CH3NH3PbI3 halide perovskite layers The perovskite was prepared using the sequential deposition method. First, MAI was dissolved in 2-propanol solvent (IPA) to form 10 mg ml1 solution. A PbI2 solution (dissolved overnight in N,N-dimethylformamide at a concentration of 461 mg ml1) was spin-coated onto the ZnO MS layer at 3000 rpm for 30 s followed
After the MAPbI3 halide perovskite was prepared, 14 nm MoO3 HSL was evaporated on the samples. Then a 60 nm Au electrode was deposited on MoO3 layers using thermal evaporation method at a deposition rate of 0.8 Ǻ/s. Finally we got the device with effective area of 0.07 cm2. 2.4. Characterization The morphology and crystallinity of the samples were characterized by field emission scanning electron microscopy (FESEM, JEOL, JSM-6700F) and X-ray diffraction (XRD, D8 FOCUS X-ray diffraction), respectively. All the current-voltage (I–V) and current-time (I-T) characteristics were measured by an Agilent B1500 electrometer. The photosensitivity was measured using a photoelectric detector spectral response measurement system (DSR100, from Beijing Saifan Optoelectronics Co., Ltd.). The sample was under direct illumination, and the optical power of light was calibrated by a ultraviolet (UV)-enhanced Si detector. 3. Results and discussion In order to effectively widen the contact area between the scaffold and perovskite, ZnO microsphere needs to be optimized. For
Fig. 1. SEM Image of the ZnO MS with various dilution times of precursors, (a) 5 (2 mM/L), (b) 6 (1.67 mM/L), (c) 7 (1.43 mM/L) and (d) 8 times (1.25 mM/L). (e) The enlarged SEM image of (c). (f) the SEM image of the MAPbI3 on ZnO MS array. (g) The transmission of the ZnO MS film with various dilution times of precursors. (h) Absorption spectrum of MAPbI3/ZnO MS array structure. (i) XRD patterns of MAPbI3/ZnO MS array structure.
Y. Zhu et al. / Applied Surface Science 448 (2018) 23–29
this, the precursors concentration is a key reaction condition to control the morphology of ZnO microspheres and the SEM images of ZnO microspheres with various precursors concentration are shown in Fig. 1a–d. Through diluting the precursors concentration from 5 to 8 times, the ZnO microspheres will decrease dramatically. Also the ZnO microsphere was consist of many nanosheets, bellow which ZnO nano-mesh structure can be seen (Fig. 1e). Based on our knowledge, much of ZnO microspheres stacked will result in big series resistance and block the carrier transport. In contrast, the sample with little ZnO microspheres will be filled by few perovskite particles, which will generate little photocurrent. So the perfect perovskite scaffold should be a monolayer and uniformly distributed ZnO microspheres on ZnO mesh nanosheet, which
25
would effectively utilize the ultrahigh surface areas of the ZnO microspheres and decrease the series resistance of devices. Thus, the solution with the six-time dilution of precursor solution may be the best. Above ZnO microspheres, the MAPbI3 perovskite layer was seen clearly with the grain size of 500–700 nm (Fig. 1f). And the ZnO microspheres were surrounded by perovskite and some perovskite grains penetrate between the nanospheres successfully, showing good contact between ZnO microspheres and perovskite. In addition, an over 80% transmittance of the ZnO microsphere film prepared with various dilution precursor solution in visible region is obtained as shown in Fig. 1(g), indicating most visible light can be absorbed by perovskite. Fig. 1 h shows the absorption spectra of the ZnO MSs /MAPbI3 ranging from 300 to 800 nm. The
Fig. 2. (a) Schematic illustration of the perovskite PD. (b) The schematic band diagram of the device. The I-V curve of the device with various dilution times of precursors, (c) 5 (2 mM/L), (d) 6 (1.67 mM/L), (e) 7 (1.43 mM/L) and (f) 8 times (1.25 mM/L).
26
Y. Zhu et al. / Applied Surface Science 448 (2018) 23–29
Fig. 3. (a) I-T curves of the device with various dilution times under UV light with the light intensity of 2 mW/cm2. (b) On/off ratio image of the device with various dilution times under UV light with the light intensity of 2 mW/cm2. Wavelength-dependent R (c) and Dk (d) at 0 V. (e) I-V curves of the devices prepared by 1.67 mM/L solution under various monochromatic light with light intensity of 1.6 mW/cm2.
absorption spectrum of the MAPbI3 on ZnO shows a strong absorption from the near-IR region to 300 nm, which may result in a wide response in this region for a broadband photodetector. The XRD patterns revealed in Fig. 1i match well with a tetragonal perovskite structure with little addition of PbI2 whose affraction peak located
at 12.70°, the moderate residual of PbI2 could deliver stable and high performance of device [29]. Structure diagram of ZnO MSs/MAPbI3/MoO3 photodetector was illustrated in Fig. 2a and b shows the schematic band diagram of the device. When the device is irradiated by light, perovskite
Table 1 The performance parameters of perovskite-based PDs in this and previously reported work.
*
Structure
On/off ratio
Responsivity (mA/W)
Detectivity (1011 Jones)
Rise time (s)
Delay time (s)
On/off ratio
Device 1* Device 2* Device 3* Device 4* ITO/ CH3NH3PbI3/ITO ZnO/CsPbBr3 CH3NH3PbBr3 nanowire TiO2/CH3NH3PbBr3
150 1400 362 255 173 12.86 61.9 <10
29 48 12 17 160 11.5 – 11.5
1.8 4.5 3.2 1.9 – – – –
– 0.014 – – 2.2 0.409 0.12 2.3
– 0.012 – – 0.3 0.0179 0.086 2.76
This This This This 32 33 34 35
Device 1, 2, 3 and 4 is the device with diluting precursor solution for 5 (2 mM/L), 6 (1.67 mM/L), 7 (1.43 mM/L) and 8 times (1.25 mM/L), respectively.
work work work work
Y. Zhu et al. / Applied Surface Science 448 (2018) 23–29
film will absorb photons and generate carrier (when the photons energy is larger than the band gap of semiconductor), and photogenerated electron-hole pairs will be by ESL and HSL, generating photocurrent, which is the principle of the self-powered device. Fig. 2c–f are the I-V curves of the device with various dilution times of precursors and all devices show good photovoltaic performance. We checked the short current (Isc) of the device, which increases with increasing dilution times and then decrease with high dilution times. The biggest Isc is 6.66 lA for the device prepared by 1.67 mM/L solution. In addition, compared to high-fold dilution, the device with low-fold dilution solution shows more smooth IV curves, showing that more ZnO MSs will benefit the interface contact between ZnO and perovskite. We next study the time response properties of the device with various dilution at zero bias. The I-T curves (Fig. 3a) show that all devices have good photoresponse with fast rise and fall speed. Similar to above, the device prepared by 1.67 mM/L solution shows best photoresponse characteristic. Based on this I-T curves, the on/off ratio is extracted and shown in Fig. 3b. We can see clearly that the device prepared by 1.67 mM/L solution shows biggest on/off ratio with the value as high as 1400, much higher than that of the other devices. The spectral R and detectivity (Dk) are two key parameters to characterize sensitivity of photodetectors [30,31], which are defined by the equations
R¼
J ph Llight
R Dk ¼ pffiffiffiffiffiffiffiffiffiffiffiffiffiffi 2qJdark
ð1Þ
ð2Þ
27
where Jph is the photocurrent density of the photodetectors, Llight is the applied optical power density, q is electron charge, and Jdark is dark current density, respectively. Seen from Fig. 3c and d, all of the photodetectors have a wide response spectrum ranging from 300 to 800 nm which due to the absorption characteristics of ZnO and MAPbI3 perovskite. However, the responsivity and detectivity of the device prepared by 1.67 mM/L solution, measured without applied voltages, are higher than those of the other devices. In addition, the responsivity and detectivity show a increase trend with decreasing the wavelength and reach a biggest value of 48 mA/W at around 380 nm, which may be attributed to ZnO. Furthermore, at the whole response wavelength the detectivity of the device prepared by 1.67 mM/L solution is above 1011 Jones (1 Jone = 1 cm Hz/W) and the biggest value is about 4.5 1011 Jones at around 380 nm. These results are comparable with the previous work [13,32–34] and the detailed comparison is shown in Table 1. Note that because of the effective absorption for ZnO microsphere in UV region, our device showed a significant UV detection performance. Fig. 3e is the I-V curves of the devices prepared by 1.67 mM/L solution under various monochromatic light with light intensity of 1.6 mW/cm2, showing our devices have a wide response spectrum ranging from 300 to 800 nm, which is consistent with the responsivity curves. From above, the device prepared by 1.67 mM/L solution displays best performance and here the detailed other performance is shown. Under various light intensity, the device shows obviously distinguishable I-V curves (Fig. 4a), displays that the photoresponse is actually dependent on the incident light intensity, which is reasonable in that stronger illumination will generate more photon-excited electron–hole pairs, and therefore leads to higher photocurrent in the circuit. It was also observed that the photocur-
Fig. 4. The performance of the device prepared by 1.67 mM/L solution. (a) I-V curves of the devices at various incident light intensity. (b) The dependence of photocurrent on operating light intensity at 0 V. (c) The dependence of photocurrent on operating time at 0 V. (d) The fast response time test.
28
Y. Zhu et al. / Applied Surface Science 448 (2018) 23–29
rent was highly related to bias voltage. We further checked the photocurrent of the detector at zero bias (Fig. 4b), which increases linearly with increasing light intensity and then reaches saturation with high light intensity (>2.5 mW/cm2). The saturated photocurrent demonstrates that the absorption capacity of the material reaches the limitation. Furthermore, the dependence of photocurrent on operating time at 0 V for the device is shown in Fig. 4c, which illustrates the device has good stability under illumination and fast time response characteristic. When the light is on, the photocurrent changes very clearly and ranges from nA to lA level. In addition, under illumination for about 800 s, the photocurrent has no attenuation and after that it can also exhibit well on/off photo switching behavior. Its detailed time response is illustrated in Fig. 4d and it can be seen that the value of rise and delay time is about 14 and 12 ms, respectively. Our device showed very good performance, we think the main reason is attributed to the ZnO MS scaffold. In the ZnO MS scaffold, many ZnO MSs are composed of nanosheets, which will beneficial for the cover of perovskite on ZnO, obtain more contact interfaces between ZnO and perovskite. Under light, much of photons absorbed by perovskite will generate many photogenerated carriers, which will be separated easily due to the increased interface. In addition, under the ZnO MSs there is ZnO mesh structure, which will block the perovskite to contact with FTO directly and can facilitate the transport of carrier. So our novel ZnO MS structure is very crucial for the good performance of the perovskite PDs. 4. Conclusion In summary, a self-powered CH3NH3PbI3 PD based on ZnO MS array scaffold was reported. Through SEM images, a ZnO microsphere array constituted by many nanosheets can be seen on ZnO mesh structure. Based on this novel structure, we first fabricated CH3NH3PbI3 photodetector with ZnO MS as the electron selective layer and MoO3 hole selective layer. Under light, the PDs showed the detection wavelength ranges from 300 to 800 nm, the responsivity values up to of 48 mA/W, detectivity values as large as 4.5 1011 Jones, on/off ratio up to 1400, and rise and fall time bellow 14 ms. These performances are comparable with the reported perovskite PDs. Acknowledgements This work is supported in part by the National Natural Science Foundation of China (No. 51372075). References [1] M. Saliba, T. Matsui, K. Domanski, J.Y. Seo, A. Ummadisingu, S.M. Zakeeruddin, J.P. Correa-Baena, W.R. Tress, A. Abate, A. Hagfeldt, M. Grätzel, Incorporation of rubidium cations into perovskite solar cells improves photovoltaic performance, Science 354 (6309) (2016) 206–209. [2] N. Arora, M.I. Dar, A. Hinderhofer, N. Pellet, F. Schreiber, S.M. Zakeeruddin, M. Grätzel, Perovskite solar cells with CuSCN hole extraction layers yield stabilized efficiencies greater than 20%, Science 28 (2017) eaam5655. [3] D. Bi, C. Yi, J. Luo, J.D. Décoppet, F. Zhang, S.M. Zakeeruddin, X. Li, A. Hagfeldt, M. Grätzel, Polymer-templated nucleation and crystal growth of perovskite films for solar cells with efficiency greater than 21%, Nat. Energy 1 (2016) 16142. [4] D. Zhao, Y. Yu, C. Wang, W. Liao, N. Shrestha, C.R. Grice, A.J. Cimaroli, L. Guan, R. J. Ellingson, K. Zhu, X. Zhao, Low-bandgap mixed tin–lead iodide perovskite absorbers with long carrier lifetimes for all-perovskite tandem solar cells, Nat. Energy 2 (2017) 17018. [5] L. Meng, E.P. Yao, Z. Hong, H. Chen, P. Sun, Z. Yang, G. Li, Y. Yang, Pure formamidinium-based perovskite light-emitting diodes with high efficiency and low driving voltage, Adv. Mater. 29 (4) (2017) 1603826. [6] J. Feng, X. Yan, Y. Liu, H. Gao, Y. Wu, B. Su, L. Jiang, Crystallographically aligned perovskite structures for high-performance polarization-sensitive photodetectors, Adv. Mater. 29 (16) (2017) 1605993.
[7] H. Zhou, J. Mei, M. Xue, Z. Song, H. Wang, High-stability, self-powered perovskite photodetector based on a CH3NH3PbI3/GaN heterojunction with C60 as an electron transport layer, J. Phys. Chem. C 121 (39) (2017) 21541– 21545. [8] P. Liu, X. He, J. Ren, Q. Liao, J. Yao, H. Fu, Organic-inorganic hybrid perovskite nanowire laser arrays, ACS Nano 11 (6) (2017) 5766–5773. [9] L. Dou, Y.M. Yang, J. You, Z. Hong, W.H. Chang, G. Li, Y. Yang, Solutionprocessed hybrid perovskite photodetectors with high detectivity, Nature Commun. 5 (2014) 5404. [10] S. Tong, J. Sun, C. Wang, Y. Huang, C. Zhang, J. Shen, H. Xie, D. Niu, S. Xiao, Y. Yuan, J. He, High-performance broadband perovskite photodetectors based on CH3NH3PbI3/C8BTBT heterojunction, Adv. Electron. Mater. 3 (7) (2017) 1700058. [11] S. Tong, H. Wu, C. Zhang, S. Li, C. Wang, J. Shen, S. Xiao, J. He, J. Yang, J. Sun, Y. Gao, Large-area and high-performance CH3NH3PbI3 perovskite photodetectors fabricated via doctor blading in ambient condition, Org. Electron. 49 (2017) 347–354. [12] S. Li, S. Tong, J. Yang, H. Xia, C. Zhang, C. Zhang, J. Shen, S. Xiao, J. He, Y. Gao, B. Yang, High-performance formamidinium-based perovskite photodetectors fabricated via doctor-blading deposition in ambient condition, Org. Electron. 47 (2017) 102–107. [13] H. Lu, W. Tian, F. Cao, Y. Ma, B. Gu, L. Li, A self-powered and stable allperovskite photodetector-solar cell nanosystem, Adv. Funct. Mater. 26 (8) (2016) 1296–1302. [14] L. Shen, Y. Fang, D. Wang, Y. Bai, Y. Deng, M. Wang, Y. Lu, J. Huang, A selfpowered, sub-nanosecond-response solution-processed hybrid perovskite photodetector for time-resolved photoluminescence-lifetime detection, Adv. Mater. 28 (48) (2016) 10794–10800. [15] M.I. Saidaminov, M.A. Haque, J. Almutlaq, S. Sarmah, X.H. Miao, R. Begum, A.A. Zhumekenov, I. Dursun, N. Cho, B. Murali, O.F. Mohammed, Inorganic lead halide perovskite single crystals: phase-selective low-temperature growth, carrier transport properties, and self-powered photodetection, Adv. Opt. Mater. 5 (2) (2017) 1600704. [16] H. Fang, Q. Li, J. Ding, N. Li, H. Tian, L. Zhang, T. Ren, J. Dai, L. Wang, Q. Yan, A self-powered organolead halide perovskite single crystal photodetector driven by a DVD-based triboelectric nanogenerator, J. Mater. Chem. C 4 (3) (2016) 630–636. [17] W. Wang, D. Zhao, F. Zhang, L. Li, M. Du, C. Wang, Y. Yu, Q. Huang, M. Zhang, L. Li, J. Miao, Highly sensitive low-bandgap perovskite photodetectors with response from ultraviolet to the near-infrared region, Adv. Funct. Mater. 27 (42) (2017). [18] B.R. Sutherland, A.K. Johnston, A.H. Ip, J. Xu, V. Adinolfi, P. Kanjanaboos, E.H. Sargent, Sensitive, fast, and stable perovskite photodetectors exploiting interface engineering, Acs Photonics 2 (8) (2015) 1117–1123. [19] J. Qiu, Y. Qiu, K. Yan, M. Zhong, C. Mu, H. Yan, S. Yang, All-solid-state hybrid solar cells based on a new organometal halide perovskite sensitizer and onedimensional TiO2 nanowire arrays, Nanoscale 5 (8) (2013) 3245–3248. [20] Y. Sanehira, Y. Numata, M. Ikegami, T. Miyasaka, Photovoltaic properties of two-dimensional (CH3(CH2)3NH3)2PbI4 perovskite crystals oriented with TiO2 nanowire array, Chem. Lett. 46 (2017) 1204. [21] J. Huang, M. Wang, L. Ding, F. Igbari, X. Yao, Efficiency enhancement of MAPbIxCl 3 x based perovskite solar cell by modifying the TiO2 interface with silver nanowires, Sol. Energy 130 (2016) 273–280. [22] S.S. Mali, C.S. Shim, H.K. Park, J. Heo, P.S. Patil, C.K. Hong, Ultrathin atomic layer deposited TiO2 for surface passivation of hydrothermally grown 1D TiO2 nanorod arrays for efficient solid-state perovskite solar cells, Chem. Mater. 27 (5) (2015) 1541–1551. [23] H. Zhou, Z. Song, P. Tao, H. Lei, P. Gui, J. Mei, H. Wang, G. Fang, Self-powered, ultraviolet-visible perovskite photodetector based on TiO2 nanorods, RSC Adv. 6 (8) (2016) 6205–6208. [24] M.S. Seo, I. Jeong, J.S. Park, J. Lee, I.K. Han, W.I. Lee, H.J. Son, B.H. Sohn, M.J. Ko, Vertically aligned nanostructured TiO2 photoelectrodes for high efficiency perovskite solar cells via a block copolymer template approach, Nanoscale 8 (22) (2016) 11472–11479. [25] M. Krbal, H. Sopha, V. Podzemna, S. Das, J. Prikryl, J.M. Macak, TiO2 nanotube/ chalcogenide-based photoelectrochemical cell: nanotube diameter dependence study, J. Phys. Chem. C 121 (11) (2017) 6065–6071. [26] X. Wang, S.A. Kulkarni, Z. Li, W. Xu, S.K. Batabyal, S. Zhang, A. Cao, L.H. Wong, Wire-shaped perovskite solar cell based on TiO2 nanotubes, Nanotechnology 27 (20) (2016) 20LT01. [27] H.S. Kim, J.W. Lee, N. Yantara, P.P. Boix, S.A. Kulkarni, S. Mhaisalkar, M. Grätzel, N.G. Park, High efficiency solid-state sensitized solar cell-based on submicrometer rutile TiO2 nanorod and CH3NH3PbI3 perovskite sensitizer, Nano Lett. 13 (6) (2013) 2412–2417. [28] N. Alwadai, M.A. Haque, S. Mitra, T. Flemban, Y. Pak, T. Wu, I. Roqan, Highperformance ultraviolet-to-infrared broadband perovskite photodetectors achieved via inter-/intraband transitions, ACS Appl. Mater. Interfaces 9 (43) (2017) 37832–37838. [29] Q. Jiang, Z. Chu, P. Wang, X. Yang, H. Liu, Y. Wang, Z. Yin, J. Wu, X. Zhang, J. You, Planar-structure perovskite solar cells with efficiency beyond 21%, Adv. Mater. 29 (46) (2017) 1703852. [30] H. Zhou, P. Gui, Q. Yu, J. Mei, H. Wang, G. Fang, Self-powered, visible-blind ultraviolet photodetector based on n-ZnO nanorods/i-MgO/p-GaN structure light-emitting diodes, J. Mater. Chem. C 3 (5) (2015) 990–994.
Y. Zhu et al. / Applied Surface Science 448 (2018) 23–29 [31] L. Yang, H. Zhou, M. Xue, Z. Song, H. Wang, A self-powered, visible-blind ultraviolet photodetector based on n-Ga: ZnO nanorods/p-GaN heterojunction, Sens. Actuators, A 267 (2017) 76–81. [32] C. Li, C. Han, Y. Zhang, Z. Zang, M. Wang, X. Tang, J. Du, Enhanced photoresponse of self-powered perovskite photodetector based on ZnO nanoparticles decorated CsPbBr 3 films, Sol. Energy Mater. Sol. Cells 172 (2017) 341–346.
29
[33] S. Zhuo, J. Zhang, Y. Shi, Y. Huang, B. Zhang, Self-template-directed synthesis of porous perovskite nanowires at room temperature for high-performance visible-light photodetectors, Angew. Chemie Int. Ed. 54 (19) (2015) 5693– 5696. [34] M. Cao, J. Tian, Z. Cai, L. Peng, L. Yang, D. Wei, Perovskite heterojunction based on CH3NH3PbBr 3 single crystal for high-sensitive self-powered photodetector, Appl. Phys. Lett. 109 (23) (2016) 233303.