The conversion efficiency (η) of organic solar cells (OSCs) constructed with ITO/ZnO/P3HT:PCBM/PEDOT:PSS/Ag is improved by incorporating Al into ZnO films (AZO) as electron transport layers (ETLs). Compared with ZnO films, AZO-based OSCs enhance η by ∼13.9% via improving short-circuit photocurrent density from 10.73 to 11.12 mA cm−2 and fill factor from 53.7% to 60.8%. Doping Al into ZnO ETLs not only optimizes band alignment between organic active layers and ETLs and increases carrier concentration, conductivity, and bandgap of ZnO films facilitating more light into OSCs but also improves the absorption of P3HT by promoting the molecular ordering of P3HT.

We demonstrated a promising route to enhance the performance of inverted organic photovoltaic (OPV) devices by the incorporation of CuGaSe2 (CGS) quantum dots (QDs) into the ZnO buffer layer of P3HT:PCBM-based devices. The modification of QDs provides better band alignment between the organic/cathode interface, improves ZnO crystal quality, and increases photon absorption, leading to more effective carrier transport/collection. By employing this energy-harvesting scheme, short-circuit current density, open-circuit voltage, and fill factor of the OPV device after CGS QD modification are improved by 9.43%, 7.02% and 6.31%, respectively, giving rise to a 23.8% enhancement in the power conversion efficiency.