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Electron transport material effect on performance of perovskite solar cells based on CH3NH3GeI3
Optical Materials xxx (xxxx) xxx
Contents lists available at ScienceDirect
Optical Materials journal homepage: http://www.elsevier.com/locate/optmat
Electron transport material effect on performance of perovskite solar cells based on CH3NH3GeI3 Nacereddine Lakhdar *, Abdelkader Hima Department of Electrical Engineering, Fac. Technology, University of El Oued, El Oued, 39000, Algeria
A R T I C L E I N F O
A B S T R A C T
Keywords: Perovskite solar cell Ge-based perovskite material J-V characteristics 1D- SCAPS
Recently, organic-inorganic perovskite-based solar cells have become promising devices due to their unique proprieties in photovoltaic field. In this scenario, several studies focusing on perovskite solar cells based on Pbperovskite layer. However, the factor of toxicity and stability of these devices is the main challenge to the progress in commercial production. In this study, a numerical modeling of perovskite solar cells using an alternative candidate which is Germanium as a perovskite material. This later is investigated in order to over come the toxicity and stability effects on perovskite solar cells, and they exhibit similar photovoltaic perfor mances as Pb-perovskite solar cells. Therefore, the effect of different kinds of electron transporting layer (ETL) materials on Ge-perovskite solar cell design is studied and investigated to enhance the conversion efficiency of perovskite devices. The obtained simulation results illustrate that perovskite solar cells based on C60 as ETL exhibit 13.5% of power conversion efficiency compared to that with other ETL materials. Thus, inserting C60 in perovskite solar cell design possibly will be considered as novel designing for future Ge-perovskite solar cells. The numerical simulation was performed using 1D-Solar Cell Capacitance Simulator (1D- SCAPS).
1. Introduction As technology advances, there is an international growing need for renewable sources of energy, especially with global concerns about the depletion of fossil resources. Renewable energies allow the provision of permanent resources, and researchers need only expand the circle of research to take advantage of these natural resources. One of the most promising renewable energies is the solar energy [1–3]. Accordingly, significant effort is required to develop a new solar cell technology with increased power conversion efficiency (PCE) and reduced processing costs. Recently, organic/inorganic halide perovskite solar cells have inherent advantages such as high absorption coefficient, long carrier-diffusion length, high carrier mobility, easy fabrication in various areas and satisfying above proprieties [4–6]. These make them very attractive for future solar cell technologies. However, the first perovskite solar cell has been developed by Kojima et al. from the Tokyo-based group of Tsutomu Miyasaka with a PCE of 2.2% in 2006 [7] and after few years they enhance it to 3.8% [8]. Therefore, in less than one decade, perovskite-based solar cell jumped to a PCE of 25.2% in 2019 [9]. To improve the performance of perovskite-based solar cell, enhancement in the device structure and perovskite material is the key
solution. Several studies are focused on use of perovskite solar cells with perovskite material based on methylammonium lead tri-iodide (MAPbI3). This later is composed of ABX3 structure, where A repre sents methylammonium (MA, CH3NH3), B is the lead (Pb) and X rep resents a halide material anion, iodide (I). Despite the high performance provided by lead halide perovskite material, the factor of instability and toxicity may hamper its commercial production [10–13]. The better way about improving these factors, an alternative candidate ecologic perovskite material is introduced and replacing the Pb-perovskite. The Ge-perovskite material may potentially provide analogous photovoltaic performances similar to Pb-perovskite devices. In this context, our work presents numerical simulations of lead free methylammonium germa nium tri-iodide (MAGeI3)-based solar cell using 1D-Solar Cell Capaci tance Simulator (1D-SCAPS) developed at the Department of Electronics and Information Systems (ELIS), University of Gent, Belgium which is a one dimensional solar cell simulator based on the drift diffusion physical model [14]. The photovoltaic performances of Ge-perovskite solar cell is compared to that of Pb-perovskite solar cell and the obtained results are validated by experimental ones taken from literature [21] showing a good agreement between them. Therefore, the work is extended to study and investigate the ETL material effect on Ge-perovskite solar cell design
* Corresponding author. E-mail addresses: [email protected], [email protected] (N. Lakhdar). https://doi.org/10.1016/j.optmat.2019.109517 Received 14 October 2019; Received in revised form 6 November 2019; Accepted 7 November 2019 0925-3467/© 2019 Elsevier B.V. All rights reserved.
Please cite this article as: Nacereddine Lakhdar, Abdelkader Hima, Optical Materials, https://doi.org/10.1016/j.optmat.2019.109517
N. Lakhdar and A. Hima
Optical Materials xxx (xxxx) xxx
Fig. 2. J-V characteristics of both simulated and experimental CH3NH3PbI3based solar cell measured under reverse voltage. Table 2 Electrical parameters of both simulated and experimental CH3NH3PbI3-based solar cell.
Fig. 1. p-i-n perovskite solar cell structure. Table 1 Material property for each layer of perovskite solar cell.
Eg (eV)
χ (eV)
3
Nc (cm ) Nv (cm 3) ND (cm 3) NA (cm 3)
εr μn (cm2V
1
μh (cm2V
1
s
1 1
)
s ) Defect density
ITO
PEDOT: PSS
MAPbI3
MAGeI3
PCBM
3.65 4.8 5.8 � 1018 1018 1020 0 8.9 10
1.6 3.4 1022 1022 1022 0 3 4.5 � 10
1.55 3.75 2.2 � 1015 2.2 � 1017 1014 5 � 1016 6.5 2
1.9 3.98 1016 1015 109 109 10 16.2
2 3.9 2.5 � 1021 2.5 � 1021 2.93 � 1017 0 3.9 0.02
10
9.9 � 10
5
2
10.1
0.02
2.5 � 10
15
–
4
16
1.5 � 10
10
14
Structures
Jsc (mA/ cm2)
Voc (V)
FF (%)
PCE (%)
CH3NH3PbI3-based solar cell (simulated) CH3NH3PbI3-based solar cell (experimental results [21])
20.08
0.87
75.28
13.22
18.2
0.93
71.2
12.05
simulation studies [15–19] are summarized in Table 1. The pre-factor values, Aα, of both ETL and HTL is set to 105 to achieve the desired curve of absorption coefficient (α) which calculated using the following expression:
α ¼ Aα (hv.Eg)1/2.
(1)
Besides, optical models used for different PAL materials are taken from experimental results found in literatures [11,20]. To investigate and study the Ge-perovskite solar cells, numerical simulations are performed to various p-i-n perovskite structures in order to show the influence of each perovskite material on perovskite solar cell performances. Using the methylammonium lead iodide (MAPbI3) as perovskite material in p-i-n perovskite design, simulation results is compared with experimental ones found in literature [21]. Then, the lead-perovskite layer is changed into germanium-perovskite material at the same p-i-n perovskite design showing the effect of Ge-perovskite material on electrical performance of perovskite solar cell. In addition, the ETL material effect on Ge-perovskite solar cell performance is studied and investigated in order to ameliorate the power conversion of solar cell. Moreover, the appropriate ETL material-based perovskite structure may be considered as novel designing for future Ge-perovskite solar cells.
1 � 1015
in order to enhance the electrical performances of solar cell. Moreover, the obtained results might indicate a suitable ETL material for improving the photovoltaic performance of solar cells based on Ge-perovskite material. 2. Device structure and methodology The basic perovskite solar cell p-i-n structure is presented in Fig. 1. It consists of three different layers, a perovskite absorbing layer (PAL) which is sandwiched between an electron transporting layer (ETL) and a hole transporting layer (HTL). The PAL represents one of both perovskite materials, MAPbI3 or MAGeI3. Whereas, the PEDOT:PSS is used as HTL and various material types are inserted as ETL. In perovskite devices, ETL is connected at metal back contact (Ag) and HTL at the transparent conducting indium tin oxide (ITO). Note that the structure is illuminated under AM1.5G solar spectrum with 100 mW/cm2 incident power density. In order to carry out our simulations, different parameter materials related to each layer and collected from recent experimental and
3. Results and discussions Numerical modeling was carried out using 1D-SCAPS software and including various material proprieties given in Table 1 and Table 4. Firstly, the p-i-n solar cell structure, ITO/PEDOT:PSS/MAPbI3/PCBM/ Ag, based on Pb-perovskite material and corresponds to layer thick nesses of 30 nm, 400 nm and 30 nm for HTL, PAL and ETL, respectively is studied and analyzed. Fig. 2 plots the J-V characteristics of both simulated and experimental Pb-based perovskite solar cell structure measured under reverse voltage. As can be seen from the figure, the 2
N. Lakhdar and A. Hima
Optical Materials xxx (xxxx) xxx
Table 3 Optimized performance of CH3NH3GeI3-based solar cell. Ge-based perovskite solar cell Parameters Thickness (nm)
No-optimized design 50 50 400 20.66 0.87 59.79 10.79
ETL HTL PVK
Jsc (mA/cm2) Voc (V) FF (%) PCE (%)
Optimized design 50 50 650 23.07 0.87 55.37 11.16
Fig. 3. J-V characteristic of no-optimized CH3NH3GeI3-based solar cell.
Fig. 5. Conversion ETL materials.
efficiency
against
absorber
thickness
for
diverse
Ge-based perovskite device shows analogous photovoltaic performance comparable to Pb-based perovskite device. To obtain strongly performance of Ge-based perovskite solar cell with more reproducibility and high stability, diverse kinds of ETL ma terials effect such as IGZO, SnO2, C60, TiO2 and ZnO are studied and results are compared to PCBM. Therefore, the material proprieties of different ETL taken from literature [22–28] are given in Table 4. Using the same optimization method mentioned above, our simula tion is performed on the power conversion efficiency as function of absorber layer thickness for different types of ETLs in order to find the optimum absorber thickness. The optimized thicknesses of both absorber and ETL layers which give the higher PCE for various ETL materials is obtained for 650 nm and 50 nm, respectively. Evidently, the PCE increases with increasing of absorber thickness for all proposed ETL materials as illustrated in Fig. 5. This increasing is due to more photons absorbed by carrier concentration in this layer creating more electronhole pairs and led to high short-circuit current density in the device. In the case of C60, TiO2 and SnO2 materials, the power conversion
Fig. 4. Variation of J-V characteristics of no-optimized and optimized CH3NH3GeI3-based design.
obtained simulated results are very close to experimental ones taken from literature [21]. Therefore, the extracted photovoltaic parameters of both simulated and experimental results are presented in Table 2. These results indicate that no big difference between both simulated and experimental values which validate our model and the parameters used in the simulation. In second time, using p-i-n solar cell structure, ITO/PEDOT:PSS/MAGeI3/PCBM/Ag, based on Ge-perovskite material and corresponds to the layer thicknesses of 50 nm, 400 nm and 50 nm for HTL, PAL and ETL, respectively. Fig. 3 displays the variation of J-V characteristic of the Ge-perovskite solar cell. The photovoltaic param eters Jsc, Voc, FF and PCE resultant were 20.66 mA/cm2, 0.87 V, 59.79% and 10.79%, respectively. It is necessary to carry out an opti mization process of the perovskite device. This is can be down by varying the diverse layer thicknesses, absorber, HTL and ETL layers. In this context, the optimization process consists to fix two layer thick nesses and vary the remaining one. Then, in each case we select the layer thickness that gives the optimal PCE value. Fig. 4 shows the optimized J-V characteristics of the Ge-based perovskite solar cell compared to that of no-optimized structure. It is evident that the optimized perovskite device shows a noticeable enhancement in PCE from 10.79% to 11.16%. Consequently, the ob tained optimized characteristic parameters and layer thicknesses of different materials are reported in Table 3. As illustrated from the table,
Table 4 Material proprieties of different ETL materials. Eg (eV) χ (eV) Nc (cm Nv (cm ND (cm NA (cm
3
) ) ) 3 ) 3
3
εr μn (cm2V μh (cm2V
s 1) s 1) Defect density
3
1
1
IGZO
C60
SnO2
ZnO
TiO2
3.05 4.16 5 � 1018 5 � 1018 1 � 1018 0 10 15 0.1 1 � 1015
1.7 3.9 8 � 1019 8 � 1019 2.6 � 1018 0 4.2 8 � 10 2 3.5 � 10 3 1 � 1014
3.5 4 2.2 � 1017 2.2 � 1016 1 � 1017 0 9 20 10 1 � 1015
3.3 4.1 4 � 1018 1 � 1019 1 � 1018 1 � 105 9 100 25 2 � 1017
3.2 3.9 1 � 1021 2 � 1020 1 � 1019 0 9 20 10 1 � 1015
N. Lakhdar and A. Hima
Optical Materials xxx (xxxx) xxx
appropriate candidate for enhancing the performance of Ge-based de vice. Thus, introducing C60 in perovskite solar cell structure may be considered as novel designing to fabricate future Ge-perovskite solar cells.
Table 5 Photovoltaic parameters of CH3NH3GeI3-based solar cell with diverse ETLs and with PEDOT:PSS as HTL. Various ETL materials
Jsc (mA/cm2)
Voc (V)
FF (%)
PCE (%)
PCBM IGZO C60 SnO2 ZnO TiO2
0.87 0.81 0.94 0.93 0.88 0.93
23.07 23.04 23.38 23.4 20.82 23.44
55.37 54.36 61.66 60.39 60.64 60.75
11.16 10.16 13.5 13.19 11.05 13.30
Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. References [1] E. Kabir, P. Kumar, S. Kumar, A.A. Adelodun, K.-H. Kim, Solar energy: potential and future prospects, Renew. Sustain. Energy Rev. 82 (2018) 894–900. [2] E. Dickinson, Solar Energy Technology Handbook, first ed., CRC Press, 2017. [3] J. Gong, C. Li, M.R. Wasielewski, Advances in solar energy conversion, Chem. Soc. Rev. 48 (2019) 1862–1864. [4] A. Hima, N. Lakhdar, A. Saadoune, Effect of electron transporting layer on power conversion efficiency of perovskite-based solar cell: comparative study, J. Nano. Electr. Phys. 11 (2019), 01026-1-3. [5] A. HIMA, N. Lakhdar, B. Benhaoua, A. Saadoune, I. Kemerchou, F. Rogti, An optimized perovskite solar cell designs for high conversion efficiency, Superlattice Microstruct. 129 (2019) 240–246. [6] I. Kemerchou, F. Rogti, B. Benhaoua, N. Lakhdar, A. Hima, O. Benhaoua, A. Khechekhouche, Processing temperature effect on optical and morphological parameters of organic perovskite CH3NH3PbI3 prepared using spray pyrolysis method, J. Nano. Electr. Phys. 11 (2019), 03011-1-4. [7] A. Kojima, K. Teshima, T. Miyasaka, Y. Shirai, Novel Photoelectrochemical Cell with Mesoscopic Electrodes Sensitized by Lead-Halide Compounds (2) 210th ECS Meeting 397, 2006, 397397. Cancun, Mexico, October Abstract. [8] A. Kojima, K. Teshima, Y. Shirai, T. Miyasaka, Organometal halide perovskites as visible-light sensitizers for photovoltaic cells, J. Am. Chem. Soc. 131 (2009) 6050–6051. [9] National Renewable Energy Laboratory, Best research-cell efficiencies. https://www.nrel.gov/pv/assets/pdfs/best-research-cell-efficiencies.20190802. pdf. [10] B. Conings, J. Drijkoningen, N. Gauquelin, A. Babayigit, J. D’Haen, L. D’Olieslaeger, A. Ethirajan, J. Verbeeck, J. Manca, E. Mosconi, others, Intrinsic thermal instability of methylammonium lead trihalide perovskite, Adv. Energy. Mater. 5 (2015) 1500477. [11] P.-P. Sun, Q.-S. Li, L.-N. Yang, Z.-S. Li, Theoretical insights into a potential leadfree hybrid perovskite: substituting Pb 2þ with Ge 2þ, Nanoscale 8 (2016) 1503–1512. [12] Qiong Wang, Nga Phung, Diego Di Girolamo, Paola Vivo, Antonio Abate, Enhancement in lifespan of halide perovskite solar cells, Energy Environ. Sci. 12 (2019) 865–886. [13] Rui Wang, Muhammad Mujahid, Yu Duan, Zhao-Kui Wang, Jingjing Xue, Yang Yang, A review of perovskites solar cell stability, advanced functional materials. https://doi.org/10.1002/adfm.201808843, 2019. [14] M. Burgelman, K. Decock, A. Niemegeers, J. Verschraegen, S. Degrave, SCAPS manual. https://users.elis.ugent.be/ELISgroups/solar/projects/scaps/SCAPS% 20manual%20most%20recent.pdf, 2016. [15] K. Tan, P. Lin, G. Wang, Y. Liu, Z. Xu, Y. Lin, Controllable design of solid-state perovskite solar cells by SCAPS device simulation, Solid State Electron. 126 (2016) 75–80. [16] Y.-Q. Zhao, B. Liu, Z.-L. Yu, J. Ma, Q. Wan, P.-b. He, M.-Q. Cai, Strong ferroelectric polarization of CH3NH3GeI3 with high-absorption and mobility transport anisotropy: theoretical study, J. Mater. Chem. C 5 (2017) 5356–5364. [17] P. Umari, E. Mosconi, F. De Angelis, Relativistic GW calculations on CH 3 NH 3 PbI 3 and CH3NH3SnI3 perovskites for solar cell applications, Sci. Rep. 4 (2014) 4467. [18] Q.-Y. Chen, Y. Huang, P.-R. Huang, T. Ma, C. Cao, Y. He, Electronegativity explanation on the efficiency-enhancing mechanism of the hybrid inorganic–organic perovskite ABX3 from first-principles study, Chin. Phys. B 25 (2015), 027104. [19] L. Zuo, Z. Gu, T. Ye, W. Fu, G. Wu, H. Li, H. Chen, Enhanced photovoltaic performance of CH3NH3PbI3 perovskite solar cells through interfacial engineering using self-assembling monolayer, J. Am. Chem. Soc. 137 (2015) 2674–2679. [20] A.M. Leguy, Y. Hu, M. Campoy-Quiles, M.I. Alonso, O.J. Weber, P. Azarhoosh, M. Van Schilfgaarde, M.T. Weller, T. bein, J. Nelson, others, Reversible hydration of CH3NH3PbI3 in films, single crystals, and solar cells, Chem. Mater. 27 (2015) 3397–3407. [21] Z. Zhu, Y. Bai, X. Liu, C.C. Chueh, S. Yang, A.K.Y. Jen, Enhanced efficiency and stability of inverted perovskite solar cells using highly crystalline SnO2 nanocrystals as the robust electron-transporting layer, Adv. Mater. 28 (2016) 6478–6484. [22] F. Azri, M. Labed, A. Meftah, N. Sengouga, A. Meftah, Optical characterization of aIGZO thin film for simulation of a-IGZO (n)/μ-Si (p) heterojunction solar cell, Opt. Quant. Electron. 48 (2016), 391-1-16. [23] U. Mandadapu, S.V. Vedanayakam, K. Thyagarajan, Simulation and analysis of lead based perovskite solar cell using SCAPS-1D, Indian J. Sci. Technol. 10 (2017) 1–8.
Fig. 6. Current density against voltage for various ETL materials.
efficiencies achieve its values of 13.5%, 13.30% and 13.19, % respec tively, and present the highest efficiencies among other used ETL ma terials. In addition, C60, TiO2 and SnO2 seem more suitable materials for perovskite solar cell which facilitate the extraction and transportation of electrons from perovskite to front contact. However, IGZO displays the lowest PCE of 10.16% compared to the proposed ETL materials. This characteristic may be due to inadequate bands alignment between the conduction band of IGZO and the LUMO of perovskite. Thus, the opti mized obtained values of device performance for different ETL materials are summarized in Table 5. In results illustrated in Fig. 6, the J-V characteristics of Ge-perovskite solar cell for diverse kinds of ETL materials is presented. It is observed that the better photovoltaic performance is displayed by inserting C60, TiO2 and SnO2 as ETL which provide very close values of Jsc, Voc, FF and PCE as shown in Table 5. The device performance is significantly enhanced from 11.16% to 13.5% by introducing the C60 compared to PCBM. This is can be explained by the use of the appropriate ETL ma terial which could effectively improve the device stability and facilitate the electron transfer from perovskite material and hence minimizing the carrier recombination probability in perovskite cells. 4. Conclusion In this paper, Germanium-based perovskite solar cell is studied and investigated using 1D-Solar Cell Capacitance Simulator (1D-SCAPS). The obtained simulation results of Ge-based perovskite solar cell demonstrate similar photovoltaic performance compared to Pb-based perovskite solar cell and there is no big difference between both struc tures. In addition, various ETL material effects on Ge-based perovskite solar cell have been studied and discussed. The performance of Ge-based device was effectively improved by inserting C60, TiO2 and SnO2 as ETL compared to other proposed ETL materials. Therefore, the perovskite device with C60 exhibits the highest PCE of 13.5% compared to that with other ETL materials. The obtained results designate that C60 is an 4
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Optical Materials xxx (xxxx) xxx
[24] T. Minemoto, M. Murata, Impact of work function of back contact of perovskite solar cells without hole transport material analyzed by device simulation, Curr. Appl. Phys. 14 (2014) 1428–1433. [25] R. Pandey, R. Chaujar, Numerical simulations: toward the design of 27.6% efficient four-terminal semi-transparent perovskite/SiC passivated rear contact silicon tandem solar cell, Superlattice Microstruct. 100 (2016) 656–666. [26] Y. Wang, Z. Xia, J. Liang, X. Wang, Y. Liu, C. Liu, S. Zhang, H. Zhou, Towards printed perovskite solar cells with cuprous oxide hole transporting layers: a theoretical design, Semicond. Sci. Technol. 30 (2015), 054004-1-7.
[27] N.T. Satyala, W.T. Wondmagegn, R.J. Pieper, M.R. Korn, Simulation of Copper Phthalocyanine/Fullerene Heterojunction Photovoltaic Cell with and without Electron Transport Layer, ETL, 2011, https://doi.org/10.1557/PROC-1212-S0818. [28] W. Abdelaziz, A. Shaker, M. Abouelatta, A. Zekry, Possible efficiency boosting of non-fullerene acceptor solar cell using device simulation, Opt. Mater. 91 (2019) 239–245.
5
Contents lists available at ScienceDirect
Optical Materials journal homepage: http://www.elsevier.com/locate/optmat
Electron transport material effect on performance of perovskite solar cells based on CH3NH3GeI3 Nacereddine Lakhdar *, Abdelkader Hima Department of Electrical Engineering, Fac. Technology, University of El Oued, El Oued, 39000, Algeria
A R T I C L E I N F O
A B S T R A C T
Keywords: Perovskite solar cell Ge-based perovskite material J-V characteristics 1D- SCAPS
Recently, organic-inorganic perovskite-based solar cells have become promising devices due to their unique proprieties in photovoltaic field. In this scenario, several studies focusing on perovskite solar cells based on Pbperovskite layer. However, the factor of toxicity and stability of these devices is the main challenge to the progress in commercial production. In this study, a numerical modeling of perovskite solar cells using an alternative candidate which is Germanium as a perovskite material. This later is investigated in order to over come the toxicity and stability effects on perovskite solar cells, and they exhibit similar photovoltaic perfor mances as Pb-perovskite solar cells. Therefore, the effect of different kinds of electron transporting layer (ETL) materials on Ge-perovskite solar cell design is studied and investigated to enhance the conversion efficiency of perovskite devices. The obtained simulation results illustrate that perovskite solar cells based on C60 as ETL exhibit 13.5% of power conversion efficiency compared to that with other ETL materials. Thus, inserting C60 in perovskite solar cell design possibly will be considered as novel designing for future Ge-perovskite solar cells. The numerical simulation was performed using 1D-Solar Cell Capacitance Simulator (1D- SCAPS).
1. Introduction As technology advances, there is an international growing need for renewable sources of energy, especially with global concerns about the depletion of fossil resources. Renewable energies allow the provision of permanent resources, and researchers need only expand the circle of research to take advantage of these natural resources. One of the most promising renewable energies is the solar energy [1–3]. Accordingly, significant effort is required to develop a new solar cell technology with increased power conversion efficiency (PCE) and reduced processing costs. Recently, organic/inorganic halide perovskite solar cells have inherent advantages such as high absorption coefficient, long carrier-diffusion length, high carrier mobility, easy fabrication in various areas and satisfying above proprieties [4–6]. These make them very attractive for future solar cell technologies. However, the first perovskite solar cell has been developed by Kojima et al. from the Tokyo-based group of Tsutomu Miyasaka with a PCE of 2.2% in 2006 [7] and after few years they enhance it to 3.8% [8]. Therefore, in less than one decade, perovskite-based solar cell jumped to a PCE of 25.2% in 2019 [9]. To improve the performance of perovskite-based solar cell, enhancement in the device structure and perovskite material is the key
solution. Several studies are focused on use of perovskite solar cells with perovskite material based on methylammonium lead tri-iodide (MAPbI3). This later is composed of ABX3 structure, where A repre sents methylammonium (MA, CH3NH3), B is the lead (Pb) and X rep resents a halide material anion, iodide (I). Despite the high performance provided by lead halide perovskite material, the factor of instability and toxicity may hamper its commercial production [10–13]. The better way about improving these factors, an alternative candidate ecologic perovskite material is introduced and replacing the Pb-perovskite. The Ge-perovskite material may potentially provide analogous photovoltaic performances similar to Pb-perovskite devices. In this context, our work presents numerical simulations of lead free methylammonium germa nium tri-iodide (MAGeI3)-based solar cell using 1D-Solar Cell Capaci tance Simulator (1D-SCAPS) developed at the Department of Electronics and Information Systems (ELIS), University of Gent, Belgium which is a one dimensional solar cell simulator based on the drift diffusion physical model [14]. The photovoltaic performances of Ge-perovskite solar cell is compared to that of Pb-perovskite solar cell and the obtained results are validated by experimental ones taken from literature [21] showing a good agreement between them. Therefore, the work is extended to study and investigate the ETL material effect on Ge-perovskite solar cell design
* Corresponding author. E-mail addresses: [email protected], [email protected] (N. Lakhdar). https://doi.org/10.1016/j.optmat.2019.109517 Received 14 October 2019; Received in revised form 6 November 2019; Accepted 7 November 2019 0925-3467/© 2019 Elsevier B.V. All rights reserved.
Please cite this article as: Nacereddine Lakhdar, Abdelkader Hima, Optical Materials, https://doi.org/10.1016/j.optmat.2019.109517
N. Lakhdar and A. Hima
Optical Materials xxx (xxxx) xxx
Fig. 2. J-V characteristics of both simulated and experimental CH3NH3PbI3based solar cell measured under reverse voltage. Table 2 Electrical parameters of both simulated and experimental CH3NH3PbI3-based solar cell.
Fig. 1. p-i-n perovskite solar cell structure. Table 1 Material property for each layer of perovskite solar cell.
Eg (eV)
χ (eV)
3
Nc (cm ) Nv (cm 3) ND (cm 3) NA (cm 3)
εr μn (cm2V
1
μh (cm2V
1
s
1 1
)
s ) Defect density
ITO
PEDOT: PSS
MAPbI3
MAGeI3
PCBM
3.65 4.8 5.8 � 1018 1018 1020 0 8.9 10
1.6 3.4 1022 1022 1022 0 3 4.5 � 10
1.55 3.75 2.2 � 1015 2.2 � 1017 1014 5 � 1016 6.5 2
1.9 3.98 1016 1015 109 109 10 16.2
2 3.9 2.5 � 1021 2.5 � 1021 2.93 � 1017 0 3.9 0.02
10
9.9 � 10
5
2
10.1
0.02
2.5 � 10
15
–
4
16
1.5 � 10
10
14
Structures
Jsc (mA/ cm2)
Voc (V)
FF (%)
PCE (%)
CH3NH3PbI3-based solar cell (simulated) CH3NH3PbI3-based solar cell (experimental results [21])
20.08
0.87
75.28
13.22
18.2
0.93
71.2
12.05
simulation studies [15–19] are summarized in Table 1. The pre-factor values, Aα, of both ETL and HTL is set to 105 to achieve the desired curve of absorption coefficient (α) which calculated using the following expression:
α ¼ Aα (hv.Eg)1/2.
(1)
Besides, optical models used for different PAL materials are taken from experimental results found in literatures [11,20]. To investigate and study the Ge-perovskite solar cells, numerical simulations are performed to various p-i-n perovskite structures in order to show the influence of each perovskite material on perovskite solar cell performances. Using the methylammonium lead iodide (MAPbI3) as perovskite material in p-i-n perovskite design, simulation results is compared with experimental ones found in literature [21]. Then, the lead-perovskite layer is changed into germanium-perovskite material at the same p-i-n perovskite design showing the effect of Ge-perovskite material on electrical performance of perovskite solar cell. In addition, the ETL material effect on Ge-perovskite solar cell performance is studied and investigated in order to ameliorate the power conversion of solar cell. Moreover, the appropriate ETL material-based perovskite structure may be considered as novel designing for future Ge-perovskite solar cells.
1 � 1015
in order to enhance the electrical performances of solar cell. Moreover, the obtained results might indicate a suitable ETL material for improving the photovoltaic performance of solar cells based on Ge-perovskite material. 2. Device structure and methodology The basic perovskite solar cell p-i-n structure is presented in Fig. 1. It consists of three different layers, a perovskite absorbing layer (PAL) which is sandwiched between an electron transporting layer (ETL) and a hole transporting layer (HTL). The PAL represents one of both perovskite materials, MAPbI3 or MAGeI3. Whereas, the PEDOT:PSS is used as HTL and various material types are inserted as ETL. In perovskite devices, ETL is connected at metal back contact (Ag) and HTL at the transparent conducting indium tin oxide (ITO). Note that the structure is illuminated under AM1.5G solar spectrum with 100 mW/cm2 incident power density. In order to carry out our simulations, different parameter materials related to each layer and collected from recent experimental and
3. Results and discussions Numerical modeling was carried out using 1D-SCAPS software and including various material proprieties given in Table 1 and Table 4. Firstly, the p-i-n solar cell structure, ITO/PEDOT:PSS/MAPbI3/PCBM/ Ag, based on Pb-perovskite material and corresponds to layer thick nesses of 30 nm, 400 nm and 30 nm for HTL, PAL and ETL, respectively is studied and analyzed. Fig. 2 plots the J-V characteristics of both simulated and experimental Pb-based perovskite solar cell structure measured under reverse voltage. As can be seen from the figure, the 2
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Optical Materials xxx (xxxx) xxx
Table 3 Optimized performance of CH3NH3GeI3-based solar cell. Ge-based perovskite solar cell Parameters Thickness (nm)
No-optimized design 50 50 400 20.66 0.87 59.79 10.79
ETL HTL PVK
Jsc (mA/cm2) Voc (V) FF (%) PCE (%)
Optimized design 50 50 650 23.07 0.87 55.37 11.16
Fig. 3. J-V characteristic of no-optimized CH3NH3GeI3-based solar cell.
Fig. 5. Conversion ETL materials.
efficiency
against
absorber
thickness
for
diverse
Ge-based perovskite device shows analogous photovoltaic performance comparable to Pb-based perovskite device. To obtain strongly performance of Ge-based perovskite solar cell with more reproducibility and high stability, diverse kinds of ETL ma terials effect such as IGZO, SnO2, C60, TiO2 and ZnO are studied and results are compared to PCBM. Therefore, the material proprieties of different ETL taken from literature [22–28] are given in Table 4. Using the same optimization method mentioned above, our simula tion is performed on the power conversion efficiency as function of absorber layer thickness for different types of ETLs in order to find the optimum absorber thickness. The optimized thicknesses of both absorber and ETL layers which give the higher PCE for various ETL materials is obtained for 650 nm and 50 nm, respectively. Evidently, the PCE increases with increasing of absorber thickness for all proposed ETL materials as illustrated in Fig. 5. This increasing is due to more photons absorbed by carrier concentration in this layer creating more electronhole pairs and led to high short-circuit current density in the device. In the case of C60, TiO2 and SnO2 materials, the power conversion
Fig. 4. Variation of J-V characteristics of no-optimized and optimized CH3NH3GeI3-based design.
obtained simulated results are very close to experimental ones taken from literature [21]. Therefore, the extracted photovoltaic parameters of both simulated and experimental results are presented in Table 2. These results indicate that no big difference between both simulated and experimental values which validate our model and the parameters used in the simulation. In second time, using p-i-n solar cell structure, ITO/PEDOT:PSS/MAGeI3/PCBM/Ag, based on Ge-perovskite material and corresponds to the layer thicknesses of 50 nm, 400 nm and 50 nm for HTL, PAL and ETL, respectively. Fig. 3 displays the variation of J-V characteristic of the Ge-perovskite solar cell. The photovoltaic param eters Jsc, Voc, FF and PCE resultant were 20.66 mA/cm2, 0.87 V, 59.79% and 10.79%, respectively. It is necessary to carry out an opti mization process of the perovskite device. This is can be down by varying the diverse layer thicknesses, absorber, HTL and ETL layers. In this context, the optimization process consists to fix two layer thick nesses and vary the remaining one. Then, in each case we select the layer thickness that gives the optimal PCE value. Fig. 4 shows the optimized J-V characteristics of the Ge-based perovskite solar cell compared to that of no-optimized structure. It is evident that the optimized perovskite device shows a noticeable enhancement in PCE from 10.79% to 11.16%. Consequently, the ob tained optimized characteristic parameters and layer thicknesses of different materials are reported in Table 3. As illustrated from the table,
Table 4 Material proprieties of different ETL materials. Eg (eV) χ (eV) Nc (cm Nv (cm ND (cm NA (cm
3
) ) ) 3 ) 3
3
εr μn (cm2V μh (cm2V
s 1) s 1) Defect density
3
1
1
IGZO
C60
SnO2
ZnO
TiO2
3.05 4.16 5 � 1018 5 � 1018 1 � 1018 0 10 15 0.1 1 � 1015
1.7 3.9 8 � 1019 8 � 1019 2.6 � 1018 0 4.2 8 � 10 2 3.5 � 10 3 1 � 1014
3.5 4 2.2 � 1017 2.2 � 1016 1 � 1017 0 9 20 10 1 � 1015
3.3 4.1 4 � 1018 1 � 1019 1 � 1018 1 � 105 9 100 25 2 � 1017
3.2 3.9 1 � 1021 2 � 1020 1 � 1019 0 9 20 10 1 � 1015
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appropriate candidate for enhancing the performance of Ge-based de vice. Thus, introducing C60 in perovskite solar cell structure may be considered as novel designing to fabricate future Ge-perovskite solar cells.
Table 5 Photovoltaic parameters of CH3NH3GeI3-based solar cell with diverse ETLs and with PEDOT:PSS as HTL. Various ETL materials
Jsc (mA/cm2)
Voc (V)
FF (%)
PCE (%)
PCBM IGZO C60 SnO2 ZnO TiO2
0.87 0.81 0.94 0.93 0.88 0.93
23.07 23.04 23.38 23.4 20.82 23.44
55.37 54.36 61.66 60.39 60.64 60.75
11.16 10.16 13.5 13.19 11.05 13.30
Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. References [1] E. Kabir, P. Kumar, S. Kumar, A.A. Adelodun, K.-H. Kim, Solar energy: potential and future prospects, Renew. Sustain. Energy Rev. 82 (2018) 894–900. [2] E. Dickinson, Solar Energy Technology Handbook, first ed., CRC Press, 2017. [3] J. Gong, C. Li, M.R. Wasielewski, Advances in solar energy conversion, Chem. Soc. Rev. 48 (2019) 1862–1864. [4] A. Hima, N. Lakhdar, A. Saadoune, Effect of electron transporting layer on power conversion efficiency of perovskite-based solar cell: comparative study, J. Nano. Electr. Phys. 11 (2019), 01026-1-3. [5] A. HIMA, N. Lakhdar, B. Benhaoua, A. Saadoune, I. Kemerchou, F. Rogti, An optimized perovskite solar cell designs for high conversion efficiency, Superlattice Microstruct. 129 (2019) 240–246. [6] I. Kemerchou, F. Rogti, B. Benhaoua, N. Lakhdar, A. Hima, O. Benhaoua, A. Khechekhouche, Processing temperature effect on optical and morphological parameters of organic perovskite CH3NH3PbI3 prepared using spray pyrolysis method, J. Nano. Electr. Phys. 11 (2019), 03011-1-4. [7] A. Kojima, K. Teshima, T. Miyasaka, Y. Shirai, Novel Photoelectrochemical Cell with Mesoscopic Electrodes Sensitized by Lead-Halide Compounds (2) 210th ECS Meeting 397, 2006, 397397. Cancun, Mexico, October Abstract. [8] A. Kojima, K. Teshima, Y. Shirai, T. Miyasaka, Organometal halide perovskites as visible-light sensitizers for photovoltaic cells, J. Am. Chem. Soc. 131 (2009) 6050–6051. [9] National Renewable Energy Laboratory, Best research-cell efficiencies. https://www.nrel.gov/pv/assets/pdfs/best-research-cell-efficiencies.20190802. pdf. [10] B. Conings, J. Drijkoningen, N. Gauquelin, A. Babayigit, J. D’Haen, L. D’Olieslaeger, A. Ethirajan, J. Verbeeck, J. Manca, E. Mosconi, others, Intrinsic thermal instability of methylammonium lead trihalide perovskite, Adv. Energy. Mater. 5 (2015) 1500477. [11] P.-P. Sun, Q.-S. Li, L.-N. Yang, Z.-S. Li, Theoretical insights into a potential leadfree hybrid perovskite: substituting Pb 2þ with Ge 2þ, Nanoscale 8 (2016) 1503–1512. [12] Qiong Wang, Nga Phung, Diego Di Girolamo, Paola Vivo, Antonio Abate, Enhancement in lifespan of halide perovskite solar cells, Energy Environ. Sci. 12 (2019) 865–886. [13] Rui Wang, Muhammad Mujahid, Yu Duan, Zhao-Kui Wang, Jingjing Xue, Yang Yang, A review of perovskites solar cell stability, advanced functional materials. https://doi.org/10.1002/adfm.201808843, 2019. [14] M. Burgelman, K. Decock, A. Niemegeers, J. Verschraegen, S. Degrave, SCAPS manual. https://users.elis.ugent.be/ELISgroups/solar/projects/scaps/SCAPS% 20manual%20most%20recent.pdf, 2016. [15] K. Tan, P. Lin, G. Wang, Y. Liu, Z. Xu, Y. Lin, Controllable design of solid-state perovskite solar cells by SCAPS device simulation, Solid State Electron. 126 (2016) 75–80. [16] Y.-Q. Zhao, B. Liu, Z.-L. Yu, J. Ma, Q. Wan, P.-b. He, M.-Q. Cai, Strong ferroelectric polarization of CH3NH3GeI3 with high-absorption and mobility transport anisotropy: theoretical study, J. Mater. Chem. C 5 (2017) 5356–5364. [17] P. Umari, E. Mosconi, F. De Angelis, Relativistic GW calculations on CH 3 NH 3 PbI 3 and CH3NH3SnI3 perovskites for solar cell applications, Sci. Rep. 4 (2014) 4467. [18] Q.-Y. Chen, Y. Huang, P.-R. Huang, T. Ma, C. Cao, Y. He, Electronegativity explanation on the efficiency-enhancing mechanism of the hybrid inorganic–organic perovskite ABX3 from first-principles study, Chin. Phys. B 25 (2015), 027104. [19] L. Zuo, Z. Gu, T. Ye, W. Fu, G. Wu, H. Li, H. Chen, Enhanced photovoltaic performance of CH3NH3PbI3 perovskite solar cells through interfacial engineering using self-assembling monolayer, J. Am. Chem. Soc. 137 (2015) 2674–2679. [20] A.M. Leguy, Y. Hu, M. Campoy-Quiles, M.I. Alonso, O.J. Weber, P. Azarhoosh, M. Van Schilfgaarde, M.T. Weller, T. bein, J. Nelson, others, Reversible hydration of CH3NH3PbI3 in films, single crystals, and solar cells, Chem. Mater. 27 (2015) 3397–3407. [21] Z. Zhu, Y. Bai, X. Liu, C.C. Chueh, S. Yang, A.K.Y. Jen, Enhanced efficiency and stability of inverted perovskite solar cells using highly crystalline SnO2 nanocrystals as the robust electron-transporting layer, Adv. Mater. 28 (2016) 6478–6484. [22] F. Azri, M. Labed, A. Meftah, N. Sengouga, A. Meftah, Optical characterization of aIGZO thin film for simulation of a-IGZO (n)/μ-Si (p) heterojunction solar cell, Opt. Quant. Electron. 48 (2016), 391-1-16. [23] U. Mandadapu, S.V. Vedanayakam, K. Thyagarajan, Simulation and analysis of lead based perovskite solar cell using SCAPS-1D, Indian J. Sci. Technol. 10 (2017) 1–8.
Fig. 6. Current density against voltage for various ETL materials.
efficiencies achieve its values of 13.5%, 13.30% and 13.19, % respec tively, and present the highest efficiencies among other used ETL ma terials. In addition, C60, TiO2 and SnO2 seem more suitable materials for perovskite solar cell which facilitate the extraction and transportation of electrons from perovskite to front contact. However, IGZO displays the lowest PCE of 10.16% compared to the proposed ETL materials. This characteristic may be due to inadequate bands alignment between the conduction band of IGZO and the LUMO of perovskite. Thus, the opti mized obtained values of device performance for different ETL materials are summarized in Table 5. In results illustrated in Fig. 6, the J-V characteristics of Ge-perovskite solar cell for diverse kinds of ETL materials is presented. It is observed that the better photovoltaic performance is displayed by inserting C60, TiO2 and SnO2 as ETL which provide very close values of Jsc, Voc, FF and PCE as shown in Table 5. The device performance is significantly enhanced from 11.16% to 13.5% by introducing the C60 compared to PCBM. This is can be explained by the use of the appropriate ETL ma terial which could effectively improve the device stability and facilitate the electron transfer from perovskite material and hence minimizing the carrier recombination probability in perovskite cells. 4. Conclusion In this paper, Germanium-based perovskite solar cell is studied and investigated using 1D-Solar Cell Capacitance Simulator (1D-SCAPS). The obtained simulation results of Ge-based perovskite solar cell demonstrate similar photovoltaic performance compared to Pb-based perovskite solar cell and there is no big difference between both struc tures. In addition, various ETL material effects on Ge-based perovskite solar cell have been studied and discussed. The performance of Ge-based device was effectively improved by inserting C60, TiO2 and SnO2 as ETL compared to other proposed ETL materials. Therefore, the perovskite device with C60 exhibits the highest PCE of 13.5% compared to that with other ETL materials. The obtained results designate that C60 is an 4
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