Impact of Carbon Quantum Dots Incorporation in Electron Transport Layer on the Performance of CsPbBr ₃ -Based Perovskite Solar Cells

This study investigates the impact of incorporating carbon quantum dots (CQDs) into the SnO 2 electron transport layer (ETL) on the performance of all-inorganic CsPbBr 3 perovskite solar cells (PSCs). CQDs with abundant surface functional groups were synthesized hydrothermally and integrated into a low-temperature, solution-processed SnO 2 ETL at varying concentrations (0%, 2%, and 4%). Comprehensive characterization revealed that the SnO 2 :CQDs composite films exhibited enhanced optical absorption, a reduced optical bandgap, and improved film morphology with superior homogeneity and reduced pinholes. While XRD analysis confirmed that the CQDs did not alter the crystalline structure of SnO 2 , electrical characterization demonstrated a significant boost in device performance. The champion device utilizing the SnO 2 :CQDs (4%) ETL achieved a power conversion efficiency (PCE) of 9.41%, representing an 11.9% enhancement over the control device with pristine SnO 2 (8.41%). This improvement is attributed to superior charge extraction, reduced interfacial recombination, and optimized energy level alignment. This work underscores the efficacy of CQDs as a simple yet powerful interfacial modifier for advancing high-performance, inorganic PSCs.