9% Certified Efficiency Record for Carbon-Based Sb2(S,Se)3 Solar Cells Enabled by Gradient-Oxidized Treatment of CdS Electron Transport Layer

Cadmium sulfide (CdS) persists as the standard electron transport layer (ETL) in high-efficiency Sb 2 (S,Se) 3 solar cells. However, its narrow bandgap imposes critical performance limitations through parasitic short-wavelength absorption and interface mismatch. Here, this bottleneck is shattered through an innovative in situ ozone doping strategy. This approach revolutionizes CdS ETLs by simultaneously: 1) Widening the bandgap of CdS ETL to drastically suppress parasitic short-wavelength photon loss; 2) Triggering a hexagonal-to-cubic phase transition that disrupts coherent Sb 2 O 3 impurity growth during Sb 2 (S,Se) 3 deposition; and 3) Engineering an oxygen-rich, defect-resistant FTO/CdS interface (DFT-validated), thereby slashing recombination and enabling superior carrier extraction. As a result, a certified world-record power conversion efficiency of 9.0% for carbon-based Sb 2 (S,Se) 3 solar cell is achieved ( V OC of 0.4908 V, J SC of 26.88 mA cm −2 , and FF of 68.19%) using an FTO/CdS:O/Sb 2 (S,Se) 3 /PbS/carbon configuration. This work, beyond setting a new benchmark for carbon-based Sb 2 (S,Se) 3 solar cells, shows that these devices demonstrate exceptional intrinsic stability under long-term and extreme damp-heat conditions without encapsulation, thus propelling Sb 2 (S,Se) 3 technology toward commercial viability.