Environmentally friendly cathode interlayer modification on edible bio-acids with enhanced electron extraction and improved power conversion efficiency

Realizing environmental compatibility and high power conversion efficiency (PCE) are crucial in the research of organic photovoltaics towards practical application. Applying environmentally friendly bio-materials into the modification of cathode interlayer (CIL) is a feasible approach to move towards both targets. In this research, three edible bio-acids, ursolic acid, citric acid, and malic acid, are employed to modify the PDIN CIL of the organic solar cells (OSCs) with non-fullerene acceptors. Among these edible bio-acid modifiers, ursolic acid shows its excellent performance in improving interfacial contact and suppressing charge recombination. It helps to obtain a good interfacial contact and facilitates the electron extraction. As a result, the photovoltaic performance is significantly improved. The average PCE are increased from 17.58% of the control devices to 18.35% of the PDIN + Ursolic Acid based devices, with a maximum PCE of 18.54%. It is the champion efficiency among the reported applications of bio-derived materials for the CILs. This study demonstrates the successful application of edible bio-acid, which offers an effective and green approach for the CIL modification to realize highly efficient OSCs.