Influence of pH Value in Electrolyte on Photovoltaic Performance of CIGS Thin-films Prepared by Electrochemical Method

doi:10.3724/SP.J.1077.2013.12148

Abstract

Abstract:

Cu(In_1-_x,Ga_x)Se₂(CIGS) films were prepared by one-step electrodeposition method on FTO glass substrates, and the influence of electrolytic pH on the chemical composition, structure and photovoltaic performance of CIGS thin-films were studied in detail. The results showed that the stoichiometry of In and Ga in the film could be effectively regulated by changing the pH value of the electrolyte. The X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM) results showed that the CIGS thin-films had good crystallinity and uniform particle size distribution when the pH value was 2.0. The effect of different stoichiometries of the CIGS thin-films on the kinetics of photo-charges was also studied. The CIGS thin film with a stoichiometric ratio of 0.3 for Ga/(In + Ga) presented the strongest surface photovoltaic effect.

Key words: CIGS thin film, one-step electrodeposition method, pH, surface photovoltage

CLC Number:

O646

SUN Bao-Ping, PANG Shan, HU Bin-Bin, YANG Guang-Hong, WAN Shao-Ming, DU Zu-Liang. Influence of pH Value in Electrolyte on Photovoltaic Performance of CIGS Thin-films Prepared by Electrochemical Method[J]. Journal of Inorganic Materials, 2013, 28(2): 141-145.

Figures/Tables 7

Fig. 1 SEM images of CIGS thin films prepared at (a) pH=2.4, (b) pH=2.2, (c) pH=2.0 and (d) pH=1.8

Table 1 Analysis of different pH values solutions for prepared the CIGS thin film by EDS analysis (at%)

Sample	pH	Cu	In	Ga	Se	n(Cu)/n(In+Ga)	n(Ca)/n(In+Ga)
A	2.4	22.1	28.0	17.0	30.8	49.1	37.8
B	2.2	11.0	39.9	9.0	40.3	22.5	18.4
C	2.0	20.8	20.7	8.8	49.6	70.5	29.8
D	1.8	19.9	45.6	0	34.6	43.6	0

Fig. 2 XRD patterns of the CIGS thin films electrodeposited at different pH values after annealing 40 min at 500℃

Fig. 3 Surface photovoltage spectra of CIGS thin films prepared in solutions of different pH values by electrodeposition

Fig. 4 Surface photovoltage spectra of CIGS film of pH value of 2.0 by electrodeposition under different biases voltage

Fig. 5 Transient surface photovoltage spectra (532 nm) of CIGS thin films prepared in solutions of different pH values by electrodeposition

Table 2 The open-circuit photovoltage data of CIGS thin film solar cells

Electrolytic pH	2.4	2.2	2.0	1.8
V_oc/mV	7.6	55.5	66.0	47.5

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