Self-passivated CdS buffer layer for antimony sulfide solar cells

Sb2S3 has been paid extensive attentions as absorber for solar cells. Comparing with some oxides, CdS exhibits excellent compatibility to Sb2S3 therefore is most commonly used as buffer layer (BL) materials for Sb2S3 solar cells. Proper passivation can enhance the performance of CdS buffer layer thus raising the performances of Sb2S3 solar cells. Herein, we put forward a self-passivation strategy to enhance the performance of CdS by a two-step deposition process to fabricate the self-passivated CdS BL. First, we adopted spin coating combined with annealing process to prepare flaked CdS on FTO, then we performed passivation process to the CdS by depositing another layer of CdS with chemical bath deposition (CBD) method. After Sb2S3 was deposited on the self-passivated CdS by hydrothermal method, a solar cell with FTO/CdS (-90 nm)/Sb2S3 (160 nm)/Spiro-OMe-TAD(48 nm)/Ag(32 nm)structure was obtained by deposition of hole transport layer and Ag electrodes. Comparing with the single spin-coating processed CdS BL or single chemical bath deposited CdS BL, the self-passivated CdS presents better performance. The CBD process presents distinctive passivation effects to the first layer. In consequence, we obtained the highest PCE of 6.04 % in the Sb2S3 solar cells on the self-passivated CdS BL. The present work supplies a unique route to enhance the performances of CdS buffer layer.