Zinc-based electron transport materials for over 9.6%-efficient S-rich Sb 2 (S,Se) 3 solar cells

Despite the toxicity of cadmium, CdS has been used as an electron transport layer (ETL) in highly efficient Sb 2 (S,Se) 3 solar cells for a long time. In this work, a bilayer structure ETL, denoted as Zn(O,S)/CdS, has been prepared as a substitute for pure CdS in S-rich Sb 2 (S,Se) 3 solar cells. This achieves two important goals related to the current use of CdS-based Sb 2 (S,Se) 3 photovoltaics, namely, due to high transmittance and a significant reduction of CdS usage, an increase of the short circuit current density in the short-wavelength range (by about 1.5 mA cm −2 ) and a decrease of the usage of CdS (by about 75%). Interestingly, the fabricated FTO/Zn(O,S)/CdS/Sb 2 (S,Se) 3 /Spiro/Au device achieved an impressive power conversion efficiency of 9.62% and shows high stability without the light-soaking (LS) effect and hysteresis. To date, this conversion efficiency value represents the highest efficiency of all Sb-based solar cells with Cd-free or reduced-Cd ETLs based on either substrate or superstrate device configurations.