CdS treatment effects on high efficient spray-deposited Zn1-xSnxO/CIGSSe solar cell

Abstract

We investigated the wide band gap oxide Zn_1-xSn_xO (ZTO) film as a potential buffer layer for Cu(In,Ga)(S,Se)₂ (CIGSSe) solar cells. Both the CIGSSe absorber and the ZTO buffer were fabricated using a non-vacuum aqueous spray method. The ZTO-buffered cell exhibited lower power conversion efficiency (PCE) compared to the CdS-buffered cell, primarily due to surface damage to the absorber caused by the spray deposition process. To mitigate this damage, a brief CdS treatment (CdS(t)) was applied prior to the ZTO spray, forming a protective layer that not only shielded the absorber but also facilitated defect passivation in the CIGSSe absorber. With the dual buffer layer of ZTO/CdS(t), we achieved a solar cell efficiency of 13.73 %, surpassing the CdS-buffered cell's efficiency of 13.32 %. Defect characterization techniques revealed that the CdS(t) treatment effectively passivated defects in the CIGSSe absorber, while the ZTO buffer enhanced photocurrent in the blue spectrum due to its wide band gap nature, leading to enhanced open circuit voltage, short circuit current, and fill factor. Furthermore, as the temperature decreased, the PCE of the ZTO/CdS(t) solar cell increased, reaching 17.17 % at temperature of 200 K. These findings suggest that ZTO buffer combined with CdS treatment could serve as a promising buffer layer for high-efficiency chalcogenide solar cell.