Influence of annealing on microstructural and photoelectrochemical characteristics of CuSCN thin films via electrochemical process

Accepted Manuscript Influence of annealing on microstructural and photoelectrochemical characteristics of CuSCN thin films via electrochemical process Mao-Chia Huang, TsingHai Wang, Yao-Tien Tseng, Ching-Chen Wu, JingChie Lin, Wan-Yi Hsu, Wen-Sheng Chang, I-Chen Chen, Kun-Cheng Peng PII: DOI: Reference:

S0925-8388(14)02576-6 http://dx.doi.org/10.1016/j.jallcom.2014.10.147 JALCOM 32493

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Journal of Alloys and Compounds

Received Date: Revised Date: Accepted Date:

10 September 2014 24 October 2014 27 October 2014

Please cite this article as: M-C. Huang, T. Wang, Y-T. Tseng, C-C. Wu, J-C. Lin, W-Y. Hsu, W-S. Chang, I-C. Chen, K-C. Peng, Influence of annealing on microstructural and photoelectrochemical characteristics of CuSCN thin films via electrochemical process, Journal of Alloys and Compounds (2014), doi: http://dx.doi.org/10.1016/ j.jallcom.2014.10.147

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Influence of annealing on microstructural and photoelectrochemical characteristics of CuSCN thin films via electrochemical process Mao-Chia Huanga, TsingHai Wangb, Yao-Tien Tsenga, Ching-Chen Wuc, Jing-Chie Lina, d, *, Wan-Yi Hsud , Wen-Sheng Changc, I-Chen Chena, Kun-Cheng Penge

a b c

Institute of Materials Science and Engineering, National Central University, Jhongli, Taiwan 32001

Biomedical Engineering and Environment Sciences, National Tsing Hua University, Hsinchu, Taiwan 30013

Green Energy and Environment Research Laboratories, Industrial Technology Research Institute, Hsinchu, Taiwan 310 d e

Department of Mechanical Engineering, National Central University, Jhongli, Taiwan 32001

Department of Materials Engineering, Mingchi University of Technology, New Taipei City, Taiwan 24301

Thin films of p-type β-CuSCN were deposited on indium-tin oxide glass substrates via electrochemical process. Various annealing temperatures (200, 300 and 400 oC) were taken into consideration. The influence of annealing temperature on structural, optical, electrical and photoelectrochemical characteristics of β-CuSCN thin films were investigated. Results from X-ray diffraction indicated as-obtained β-CuSCN thin film was in a hexagonal close pack crystal structure. We found that the crystallographic orientation changed and the optical energy band gap slightly increased with increasing annealing temperatures. These properties made CuSCN films annealed at 400 oC a better photoelectrochemical performance with photocurrent density of about -0.39 mA/cm2 at -0.5 V vs. SCE. This value is about 8 times higher than the as-deposited CuSCN film. Observed higher photocurrent density is likely due to the intrinsic of a higher charge carrier concentration, and a lower resistance within CuSCN crystal and at CuSCN /electrolyte interface. Keywords: CuSCN; annealing effect; electrochemically deposition; photoelectrochemistry; water splitting. *Corresponding author, E-mail: [email protected]

1

1. Introduction Clean energy of hydrogen has been considered as one of potential candidates to solve nowadays urgent issues in global warming and fossil energy crisis. Photoelectrochemical (PEC) water splitting was a promising method to produce hydrogen by converting solar energy that could be further utilized 1-3. In 1972, PEC water splitting using TiO2 photocatalyst was first proposed by Honda and Fujishima 1. However, the photocatalyst of TiO2 showed a poor performance of hydrogen production. In order to improve the PEC response, various semiconductors have been widely investigated 4-13. Recently, preparation of p-type thin films have drawn a great attention because of their potential applications in light emitting diode (LED) 14, dye-sensitized solar cells (DSSCs) 15 , nanocrystalline cells (NPCs) 16, 17 and PEC water splitting 18. Among these p-type thin films, Cu (I)-based compounds such as CuSCN, Cu2O, CuAlO2, and CuI are particularly of interest 19-21

. To prepare these materials, electrochemical deposition is proven as one of the most economic and effective technique 22. In comparison with Cu2O, CuSCN possesses a wider band gap and a greater optical transparency in the visible light spectrum. In addition, fabricating a p-type CuSCN thin film directly onto n-type materials such as ZnO, TiO2 23, 24 can introduce an interesting heterojunction, which has been proven with a comparable efficiency to that of a p-n homojunction of silicon based solar cells. Among all CuSCN structures, beta hexagonal cuprous thiocyanate (β-CuSCN) possesses a very wide-band-gap absorbance (3.6 eV) 25 and a relatively higher hole conductivity (5 × 10 -4 S cm-1) 26. Along with its great chemical stability 27, β-CuSCN had been widely fabricated with many other n-type materials such as p-CuSCN/n-ZnO, p-CuSCN/Sb2S3/n-TiO2 and n-CuAlO2/p-CuSCN etc. 28-34 for solar energy application. Among all Cu (I)-based thin films, both CuSCN and Cu2O films have been successfully prepared via electrochemical deposition route 22, 35. However, post heat treatment regarding as-obtained CuSCN is barely found in the literature. Post heat treatment is a well-known process to carry out structural reorganization and is able to eliminate structural defects, tensile stress or compressive stress present in an as-deposited semiconductor material. Appropriate post heat treatment was also shown to be effective in enhancing the performance of solar cell 36 and photocatalyst 37…etc. In the present work, the CuSCN films were electrochemically deposited under room temperature in an electrolyte solution containing 0.01 M copper sulfate, 0.10 M triethanolamine, and 0.05 M potassium thiocyanate. As-deposited films were then heat-treated annealing in an evacuated tube furnace (under 2 x 10-2 Torr) under different temperatures (200, 300 and 400 oC). The annealing effect on the microstructural, PEC and electrochemical characteristics of these electrodeposited CuSCN thin films was discussed. 2. Experimental Detail 2.1 Setting of electrochemical deposition and annealing 2

Electrochemical deposition was carried out potentiostatically in a 100 mL-beaker where three electrodes were used. Glass substrate coated with indium-tin oxide (ITO, sheet resistance ~7 ohm/□, supplied by Ultimate Materials Technology Co. Ltd., Taiwan) was sliced into 30 mm × 10 mm × 1.0 mm. The upper portion of the glass specimen was glued together with carbon paste and copper lead which extended to connect with a potentiosat (EG&G 263A) and this glued region was then coated by epoxy resin to expose an area of 10 mm × 10 mm acting as the working electrode. Prior to electrochemical deposition, the ITO substrate was cleaned ultrasonically in distilled water and then blown dry by high-pressure nitrogen. A platinum-coated titanium mesh was used as the counter electrode and a SCE in connection with Haber-Luggin capillary as the reference electrode. The separation between the working and the reference electrodes was at 15 mm and 30 mm between the working and counter. A solution of 100 mL containing 0.01 M copper sulfate (CuSO4), 0.10 M triethanolamine (TEA, N(CH2CH2OH)3), and 0.05 M potassium thiocyanate (KSCN) was used as the electroplating bath. The bath was stirred with a magnetic stirrer in the electrochemical deposition process that was conducted at -0.40 V against SCE for 30 minutes under room temperature. All the potentials reported this work were versus SCE referenced scale. All the deposited samples were washed with distilled water to remove the electrolyte and dried by a stream of nitrogen gas. In the process of heat treatment, all the clean and dried as-deposited specimens were put into a vacuum (2×10-2 Torr) tube furnace by varying the temperatures at 200, 300 and 400 oC annealed for 1 h, respectively. Both of heating up rate and cooling down rate were setting at 10 oC/min. 2.2. Characterization of the as-deposited and annealed films The as-deposited and various annealed temperatures of CuSCN thin films were labeled with A, B, C and D, respectively. The surface morphology of the films was examined by using scanning electron microscopy (SEM, NOVA Nano SEM 230) at an accelerating voltage of 10 kV. Elemental analysis of the films was determined by the energy dispersive spectrometer (EDS) equipped with the SEM. Film thickness of the samples was measured by α-step (FORCE, EZstep). X-ray diffraction (XRD) patterns were measured on a D2 Phaser diffractometer (Brucker) using Cu Kα radiation (λ = 1.5418 Å) were recorded in the 2-thea range from 25o to 55° and at the scan rate of 2 degree/min. The measurement of optical transmittance was carried out by an ultra violet-visible transmittance spectra (Cary 100 Scan, Varian) equipped with a diffuse reflectance accessory (Labsphere, DRA-CA-3300) over a range of 300–800 nm and using an identical ITO-coated glass substrate as the reference. 2.3 Electrochemical analysis All PEC reactions were conducted in a home-made photoreactor equipped with a 3

water-circulating jacket at temperature of 25 oC. All electrochemical measurements were performed in a standard three-electrode system, a CuSCN film (as-deposition, annealing at 200, 300 and 400 o C) as the working photoelectrode, a saturated calomel electrode (SCE) as the reference electrode, and platinum foil as the counter electrode in 0.5 M Na2SO4 aqueous solution and a potentiostat (AUTOLAB Model PGSTAT 30). The sample was placed in the electrochemical cell at a distance of 5.0 cm from the quartz window. All samples were kept with an identical reactive area of 1.0 cm2. PEC characteristics of all the samples were measured via chopping method 38 at a scan rate of 25 mV s−1 in an applied potential range of –0.5 to +0.5 V vs. SCE. A 300 W Xe lamp (Perkin Elmer Model PE300UV) with AM 1.5 filters were used as simulated sunlight. The intensity was calibrated to 100 mW/cm2. A Silver wire was attached to the conducting layer of the working electrode with silver paste, and the back and sidewall of the samples was sealed with epoxy resin to prevent current leakage 39. Electrochemical impedance spectroscopy (EIS) was performed by applying -0.5 V vs. SCE in a frequency range of 100 to 10000 Hz with 10 mV amplitude in the dark. For Mott-Schottky plot analysis, those samples measured at the frequency of 500 Hz in the dark from -1.0 V to +0.6 V. Corresponding charge carrier concentration was extracted from the linear data fitting as follows 40:

1 2 kT   =B E − E fb −  2 2  e  C eεε 0 N D A 

(1)

where e was the electronic charge A was the surface area of the semiconductor/electrolyte interface, ND was the carrier density of the semiconductor, Efb was the flat-band potential of the semiconductor, ε was the dielectric constant of the semiconductor, and ε0 was the permittivity of vacuum, respectively. B equaled to 1 for n-type semiconductors, while B equaled to -1 for p-type semiconductors 38. According to equation (1), the slope as follows:

2 eεε 0 N D A 2

(2)

3. Results and discussion

3.1 Microstructure, morphology and composition of CuSCN thin films Fig. 1(a) revealed the corresponding cathodic arc of the potentiodynamic polarization in the used system. Once the applied voltage was dropping below -0.4 V, an obvious plateau of constant current density appeared (0.8 mA cm-2). It was then considered as the region of limiting current density of our system. We also recorded the variation of current density against time under the potential of -0.40 V and the result was shown in Fig. 1(b). From Fig. 1(b), it was aware a steady state of constant current density (0.02 mA cm-2) was reached in 300 s. We therefore confidently prepared all CuSCN thin films with applying -0.4 V for 30 minutes under room temperature. XRD patterns shown in Fig. 2(a) illustrated the CuSCN thin films. In comparison with the 4

reference β-CuSCN diffraction pattern (JCPDS 29-0581) 25, we confirmed that all films retained their β-CuSCN structure after annealing under different temperatures. No significant impurity phase appeared; however, it is obvious that relative intensity between each diffraction (mainly (101), (006) and (107) changed significantly after annealing). The intensity of diffraction at the position 27.22。, in response to (101) of CuSCN, increased with increasing annealing temperature up to 400 oC. The (006) peak at 32.51。 and (107) peak at 47.24。 where its intensity decreased as the annealing temperature increased. Intensity variation observed in XRD suggests that annealing would induce the changes in the orientation of CuSCN particles. We thus proposed that annealing temperature applied thermal energy particularly enables the development of CuSCN toward (101) direction. This leads the formation of a dense and (101) preferred orientation of CuSCN thin film. The grain size of those samples calculated from Scherrer’s formula 41: D = 0.9λ/βcosθ

(3)

where D is the grain size, β is the value of full width at half maximum (FWHM) of the (101) diffraction peak and λ is the X-ray wavelength (0.154 nm) , respectively. The calculated grain size for (101) peak shows a size of 25.0, 29.1, 35.5 and 40.0 nm for the A, B, C and D. Figure 2 (b) shows the relation between grain size and FWHM of (101). When the annealed temperature increased, the grain size of CuSCN films increased but FWHM of (101) decreased. It was unambiguous that the grain size increased along with the increasing annealed temperatures. Fig. 3 shows the surface morphology of CuSCN films of (a) as-deposited and annealed at (b) 200, (c) 300, (d) 400 oC and (e) cross section image of (a) , respectively. Fig. 3(a) showed the top view SEM image of the as-deposited CuSCN film and it appeared that CuSCN film was assembled with triangle nanoparticles with average particle size around 420 nm. Similar morphology was reported in literature but our CuSCN particles seem to be smaller in size 42. Smaller particle size could be attributed to the lower current density we applied (0.02 vs. 0.05 mA cm-2) 42. During electrodeposition, the majority of applied electrons were working on Cu2+ reduction and consequently the nucleation of cuprous hydroxides rather than on the particle growth. This might explain the appearance of observed CuSCN films stacking with smaller particles. From SEM cross section view and profilometer (shown in Table 1), the thickness of obtained CuSCN film was estimated around 550 nm. The surface morphology of these films seems to be slightly affected by the annealed temperature. The annealed samples also show triangle particle structure in Fig. 3 (b) to (d). However, as the annealed temperature increased, the average particle size increasing 630 to 960 nm. There was a difference between the particle size and grain size measurements by SEM and XRD. In SEM, the particle size was measured by the distances between the grain boundaries and the particle size may affect by some defect such as dislocation. In the XRD pattern, it was measured the crystalline region of X-ray coherently that leads to smaller grain size by Sherrer's formula 43. The thickness of various annealed temperature of CuSCN thin films shown table 1. These 5

results revealed that the thickness of all samples weren’t depending on annealed temperature. The elemental analysis on those samples by means of EDS was demonstrated in Table 1. From Table 1, all samples shows an approximately composition ratio of SCN/Cu is 1.60. The ratio apparently corresponds to a Cu deficient CuSCN film. According to the stoichiometric ratio, the chemical composition of the as-deposited film was suggested as p-type CuSCN that could be attained in the following electrochemical deposition 44 at -0.4 V 25: [Cu(SCN)]+ + e- → CuSCN

(4)

3.2 Optical and electrical properties of CuSCN films In optical properties, all of the samples have an about 80 % transmittance ranging from wavelength 400 nm to 800 nm (Fig. 4(a)). From this, we are able to estimate the optical band gap of annealed samples from transmittance spectra. Based on Beer-Lambert’s Law 6: αhν=A(Eg-hν)n

(5)

Where α is the absorption coefficient of the material, hν is the photon energy, A is constant, n was assigned either 2 for with indirect band gap material or 1/2 for direct band gap one (CuSCN in this case). Figure 4(b) revealed the plot of (αhν)2 versus photon energy for the CuSCN films with/without annealing. The band gap (Eg) of the film can be extracted by extrapolation the curve to the intercept (Fig 7). From Table 1, we noticed that the estimated Eg values were in the range 3.19 to 3.21 eV. At lower annealing temperature (＜300 oC), the band gap of CuSCN thin films have the same value of 3.19 eV. Higher annealing (≧300 oC) seems to produce CuSCN films possessing slightly higher band gap energy. Observed lower band gap energy (＜3.6 eV) should be closely related to some intrinsic defects introduced during electrodeposition 45. According to the density functional theory simulation, Cu deficient would introduce many shallow accepters leveling at about 0.2 eV above the valence band edge 21. On the other hand, another interesting feature observed is that the band gap energy slightly increased as the annealing temperature at 400 oC (Fig. 4(b)). From density functional theory calculation, it is realized that any structural distortion leads to an increase in antibonding character and thus increase the band gap energy 21. Accordingly, the variation in band gap energy is likely the consequence of the stress release during annealing. During annealing, lattice atoms acquire enough thermal energy to delocalize and to release accumulated structural stress. Such relaxation enables lattice atoms stabilize in a relatively thermodynamically stable manner. That is, less antibonding and higher bonding character. The electrical resistivity was measured by means of four-point probe and shown in Table 1. Interpreting the electrical resistivity of these samples should be very careful since it is very 6

susceptible by those of conductive substrate beneath. It is known that the electrical resistivity inside ITO structure is around 1.82×10-4 ohm cm (also shown in Table 1), which is significantly higher than our samples. The resistivity was the highest for the as-deposited film and gradually decreased with increasing the annealing temperature from 200 up to 400 oC. Further annealing releases the structural stress and makes these acceptors much more mobile and therefore decrease the resistivity. 3.3 PEC and electrochemical properties of CuSCN thin films From Fig. 5(a), it is clear that CuSCN film anneal at 400 oC possessed the highest photocurrent density over others (-0.39 mA/cm2 at -0.5 V vs. SCE). This value is about eight times higher than that without any annealing treatment. The higher photoelectrochemical response can be the result of higher charge carrier concentration as evidenced by Fig. 5(b) and Table 2. In Fig. 5(b), the Mott–Schottky plots shown that a negative slope of all samples, that is before and after annealed CuSCN films were p-type semiconductors. These results were agreement with EDS measurement. In Table 2, the slope of 400 oC annealed CuSCN thin films was -2.86×1014 which was about ten times smaller than the as-deposited sample (-2.83×1015). If we supposed the ε is a constant, the calculated hole concentration from the slope for the 400 oC annealed film should be ten times larger than that of the as-deposited film 46. The flat potentials and the onset potentials of all samples were also shown in Table 2. All samples have the same flat potential value of 0.41 V vs. SCE and the onset potential values increased from 0.34 to 0.37 V vs. SCE as the annealed temperature increased. Since no additional doping or cocatalyst was added during CuSCN thin films electrodeposition process, the variation in charge carrier concentration could thus reflect the annealed temperature effect. That is, based on above observations, effect of preferential orientation, charge carrier concentration and resistance. First, it has been reported that the highly (101) oriented CuSCN film always possessing a better carrier concentration than others with less (101) orientation 46. Second, Fig. 5(c) shows the corresponding electron impedance spectra measured at -0.5 V (vs SCE). They were fitted by a simple R1[R2Q2][R3Q3][R4Q4] equivalent circuit (Fig. 5(d)). Here, R1, R2, R3 and R4 reflect the resistance at wire/ITO glass substrate interface, ITO glass substrate/CuSCN interface, entire CuSCN layer, and CuSCN/electrolyte interface, respectively 7. Table 3 summarizes all the fitting results. As expected, we can the reasonably ignore the resistances at wire/ITO glass substrate interface in all cases. In the case with applied -0.5 V vs SCE, the R2 values of these samples decrease along with the increasing annealed temperature. The same tend appears in R3 values, which gradually decreases as the increasing annealed temperature. This implies films annealed at higher temperature tend to possessing lower resistance at ITO glass substrate/CuSCN interface and within CuSCN layer. For electrodeposited CuSCN, lower resistivity values have been reported for films with a higher (101) orientation 46. As a result, the level of resistance of entire CuSCN layer should be closely dependant on film orientation. The resistance at CuSCN/electrolyte interface (R4) 7

of as-deposited film is about two orders of magnitude higher in film annealed 400 oC, as evidenced a larger semicircle in Fig. 5(c) and Table 3. Fig. 5(e) shows that all films possess a reasonable stability. The photocurrent of all samples dropped within about 5 % over the course of 10 h. Conclusion

Thin films of p-type CuSCN could be readily electrochemical deposited on the ITO-coated glass substrate at -0.4 V versus SCE for 30 minutes at room temperature. The as-deposited and annealed films revealed the same crystal structure of β-CuSCN and annealing led to particles size change only. The SEM morphology indicated the particles in the film revealed the greatest size with increasing the annealing temperature. In XRD patterns, the intensity of (101) peak increased with increasing annealed temperature result of a higher carrier concentration of CuSCN thin film. All films revealed p-type character analyzed by Mott-Schottky plot. We found CuSCN films annealed at 400 oC possessing a better photoelectrochemical performance with photocurrent density of -0.39 mA/cm2 bias -0.5 V vs. SCE. This is likely the result of a higher charge carrier concentration, a lower resistance, and (101) preferred orientation of CuSCN thin film. Acknowledgment

The authors highly appreciate the financial support of Ministry of Science and Technology, Taiwan, under the contract of MOST103-2221-E-008-025. References [1] A. Fujishima, K. Honda, Nature 238 (1972) 37-38. [2] C. W. Lai, S. Sreekantan, J. Alloy. Compd. 547 (2013) 43-50.

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Figure captions

Fig. 1. (a) Cathodicaclly potentiodynamic polarization of ITO in the bath of copper sulfate at room temperature and (b) Cathodic current as a function of time in the process of electrodeposition of CuSCN thin film performed at -0.4 V vs. SCE. Fig. 2. (a) The X-ray diffractions of the as-deposited CuSCN film, ITO and various CuSCN films annealed at different temperatures for 1 h and (b) Variation of the grain size, FWHM of (101) peak for the CuSCN thin films. Fig. 3. Top view morphology on the scanning electron microcopy (SEM) of CuSCN film electrochemically as-deposited on ITO substrate of (a) as-deposited and annealed at (b) 200, (c) 300, (d) 400 oC; (e) with the cross section of (a). Fig. 4. (a) Transmittance spectra and (b) The plot of (αhν)2 versus photon energy for the as-deposited CuSCN thin film and the films annealed at various temperatures for 1 h. Fig. 5. (a) The photoelectrochemistry characteristics. (b) Mott–Schottky plots. (c) Nyquist diagrams. All curves represent the experimental data, and all geometric symbols shows simulated data obtained using equivalent circuits. (d) The equivalent electrical circuit used to fit all experimental data from Fig. 5(c) for CuSCN thin films. (e) Photocurrent density at -0.5 V vs. SCE as a function of time for all samples. All measurements were recorded by three electrode set-up system in 0.5 M Na2SO4 aqueous solution.

11

Fig. 1(a) and (b)

12

Fig. 2(a)

13

Fig. 2(b)

14

Fig. 3

(a)

(b)

4μ μm

(c)

4μ μm

(d)

4μ μm

4μ μm

(e)

CuSCN thickness ~550 nm ITO

1μ μm

15

Fig. 4(a)

16

Fig. 4(b)

17

Fig. 5(a)

18

Fig. 5(b)

19

Fig. 5(c) and (d)

(d)

20

Fig. 5(e)

21

Table captions Table 1. The physical properties of CuSCN thin films. Table 2. The electrochemical properties of CuSCN thin films. Table 3. Values for the equivalent circuit parameters

Table 1. The physical properties of CuSCN thin films. Annealed temperature FWHM of (101) Sample (°) (°C)

Grain Size (nm)

(nm)

b

Band gap

Resistivity

Cu

S

C

N

(eV)

(ohm cm)

ITO

--

--

--

260

--

--

--

--

--

1.82×10-4

A

--

0.64

25.0

550

38.44

19.14

22.93

19.49

3.19

7.55×100

B

200

0.55

29.1

545

38.49

19.44

22.12

19.95

3.19

5.63×10-1

C

300

0.45

35.5

544

39.54

19.55

21.26

19.65

3.19

3.28×10-1

D

400

0.40

40.0

552

39.95

19.75

20.76

19.54

3.21

8.32×10-2

a

The grain size of thin films calculated by Scherrer’s equation.

b

The thickness of thin films obtained by α-Step. The atomic molar ratio was determined by EDS.

c

a

Thickness Element composition (at.%) c

Table 2. The electrochemical properties of CuSCN thin films. Sample

Photocurrent density 2

A B C D

a b

Onset potential

Slope of Mott–Schottky plot

a

Flat potential (V vs. SCE) b

bias -0.5 V (mA/cm )

(V vs. SCE)

-0.08

0.41

-2.83×10 15

0.34

0.41

-1.51×10

15

0.35

-5.71×10

14

0.37

-2.86×10

14

0.37

-0.15 -0.29 -0.39

0.41 0.41

Onset potential obtained by photoelectrochemistry characteristics (Fig 5(a)). Flat potential obtained by Mott-Schottky plot (Fig. 5(b)).

Table 3. Values for the equivalent circuit parameters Sample

Values for the equivalent circuit parameters R1

A

R2

Q1Y0

n

3.60×102 7.49×103 1.60×10-8 3

-9

C

3.86×10

3

-10

D

3.99×102 1.75×103 3.27×10-5

B

2

3.79×10

2

2.46×10 1.31×10 2.32×10 5.34×10

0.80

R3

Q2Y0

n

1.53×104 6.03×10-11 4

-7

1.00

3

9.72×10 1.43×10

-10

0.99

3.54×102 6.77×10 -5

0.85

1.00×10 3.52×10

1.00

R4

Q3Y0

n

1.26×105 1.61×10 -9

1.00

5

-9

0.88

0.81

4

9.39×10 9.93×10

-9

0.79

1.00

4.37×103 2.69×10-10

0.45

0.78

1.05×10 2.59×10

Highlights of this work


CuSCN films was synthesized by electrochemical process.




The parameter of CuSCN films was annealing temperature.




The photoelectrochemical characteristics of CuSCN films were investigated.

22