Improving the performance of Sb₂S₃ thin-film solar cells by optimization of VTD source-substrate proximity

In this paper, Sb₂S₃ thin-film solar cells are fabricated by the vapor transport deposition (VTD) method. The effect of the source-substrate proximity on the performance of Sb₂S₃ thin-film solar cells has been investigated and comparative studies of different source-substrate proximity are carried out. The device efficiency is improved from 0.83 to 3.02% by optimizing the source-substrate proximity with the augment of open-circuit voltage, short-circuit current density and fill factor. X-ray diffraction and scanning electron microscopy studies indicate that the deposited Sb₂S₃ films can achieve optimal grain orientation, high crystallinity, and compact morphology. Moreover, the current transport mechanism is analyzed in detail from dark current density–voltage (J-V) measurements and shows the optimal sample to be least affected by Shockley-Read-Hall recombination and space-charge-limited current (SCLC). Meanwhile, temperature and light intensity-dependent open-circuit voltage measurements reveal the carrier recombination rates are lowest for the optimal cell in all regions, including the CdS/Sb₂S₃ interface, the space-charge region (SCR), and the quasi-neutral region (QNR). These can account for the efficiency enhancement of the optimal cell and can be used to facilitate the further development of Sb₂S₃ thin-film solar cells.