Application of Transparent Cobalt Sulfide Counter Electrodes in Dye-sensitized Solar Cells

doi:10.15541/jim20170490

Abstract

Abstract:

Cobalt sulfide nanomaterials are considered as important counter electrode materials for dye-sensitized solar cells. A potential reversal electrodeposition technique was applied to fabricate transparent cobalt sulfide film with fluorine-doped tin oxide glass as substrate. The experimental results demonstrate that the surface morphology of cobalt sulfide films is mainly dependent on the pH value of plating solution. The thickness of cobalt sulfide films can be effectively controlled by electrodeposition cycles. Then, cobalt sulfide films were used as counter electrodes of dye-sensitized solar cells. Electrochemical measurements prove that cobalt sulfide counter electrodes exhibit high electrocatalytic activity. In particular, under electrodeposition condition of pH 7.2 and 12 cycles, cobalt sulfide counter electrode composed of the nanosheet structure exhibits higher electrocatalytic activity than platinum electrode, due to the increase of electrocatalytic active sites. Meanwhile, remarkable photoelectrical conversion efficiency of the dye-sensitized solar cell based on cobalt sulfide counter electrode is up to 7.26% with an average value of 7.18% for ten devices, which is higher than that of the dye-sensitized solar cell equipped with platinum electrode (6.94%).

Key words: counter electrode, cobalt sulfide, potential reversal electrodeposition technique, sheet morphology

CLC Number:

TM914

JIANG Qing-Song, CHEN Ruo-Ting, LI Wen-Bo, CHENG Wen-Jie, HUANG Ye-Xiao, HU Guang. Application of Transparent Cobalt Sulfide Counter Electrodes in Dye-sensitized Solar Cells[J]. Journal of Inorganic Materials, 2018, 33(8): 832-838.

Figures/Tables 7

Fig. 1 (a-d) SEM images of Co-S films; (e) SEM and (f) TEM images of Co-S film under electrodeposition condition of pH 7.2 and 30 cycles; (g) The EDS mapping images and (h) element compositions of S-pH7.2

Fig. 2 XPS spectra of S-pH7.2 (a) Co2p; (b) S2p

Table 1 Photovoltaic performance parameters of DSC based on Co-S and Pt Ces

CE	J_SC/(mA•cm^-2)	V_OC/V	FF	η/%
Pt	15.94	0.67	0.65	6.94
S-C10	19.78	0.69	0.51	6.96
S-C12	18.47	0.69	0.57	7.26
S-C14	17.11	0.69	0.56	6.61
S-C16	16.52	0.69	0.55	6.27
S-pH5.8	14.10	0.70	0.52	5.13
S-pH6.7	16.96	0.68	0.56	6.46
S-pH7.2	18.47	0.69	0.57	7.26
S-pH7.6	11.56	0.67	0.54	4.18

Fig. 3 (a, b) J-V curves of DSC based on Co-S and Pt Ces and (c) photovoltaic parameters of DSC based on S-pH7.2 as a function of device quantity

Fig. 4 CV curves of Co-S and Pt CEs

Fig. 5 Nyquist plots of EIS for symmetrical cells with the inset in (a) showing the equivalent circuit The symbols represent experiment data, and the solid lines express fit results for EIS data.

Table 2 Fitting parameters of EIS for Co-S and Pt Ces

CEs	Pt	S-pH5.8	S-pH6.7	S-pH7.2	S-pH7.6
R_s/Ω	29.55	53.32	45.52	38.95	61.13
R_ct/Ω	17.56	31.21	25.86	16.98	237.10
Z_N/Ω	9.01	10.67	9.69	8.51	20.21

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