Ce-doped ZnO ETLs: enhancing optoelectronic properties for efficient HTL-free Cs0.10MA0.90Pb(I0.90Br0.10)3-based perovskite solar cells

Perovskite solar cells (PSCs) have gained significant attention in photovoltaics due to their remarkable efficiency improvements over the past decade. Their performance depends on the absorber layer, electron transport layer (ETL), hole transport layer (HTL), and contacts. ZnO, with a direct band gap of 3.32 eV, is widely used as an ETL because of its suitable band alignment with 10% Cs-doped MAPbI3. To minimize recombination and defects, ZnO was doped with 2, 4, and 6% Ce using the sol-gel method, and ETLs were fabricated by spin coating. At 2% Ce, the ZnO band gap decreased, crystallinity improved, defects reduced, and uniform films formed. Micro strain and dislocation density reached minimum values, enhancing crystal growth. When Cs0.10MA0.90Pb(I0.90Br0.10)3 was deposited on 2% Ce-ZnO, pinholes decreased, contact angle increased, charge extraction improved, recombination reduced, and moisture stability enhanced. HTL-free PSCs with carbon electrodes achieved a peak PCE of 16.16%, attributed to improved short-circuit current density (Jsc) and fill factor (FF).