Tri(oxyethylene)-functionalised perylene diimide: a promising interlayer material for enhanced organic photovoltaic performance†

Abstract

Interface engineering of organic semiconductors is critical for efficient charge extraction from organic photoactive layers to inorganic electrodes, which is a key factor in optimising organic solar cell performance. Incorporating polar groups into electron transport layer (ETL) materials can reduce their work function by forming appropriate dipoles between the photoactive layer and the electrode. This study reports a promising ETL material, 2,9-bis(2-(2-(2-methoxyethoxy)ethoxy)ethyl)anthra[2,1,9-def:6,5,10-d′e′f′]diisoquinoline-1,3,8,10(2H,9H)-tetraone, coded PDIAO, based on a perylene diimide (PDI) core with tri(oxyethylene) chains at the imide positions. PDIAO exhibited efficient energy level alignment and good interface contact with the active layer, facilitating efficient electron extraction. Organic photovoltaic (OPV) devices with the PM6:IT-4F active layer, a PDIAO interlayer, demonstrated enhanced performance, achieving a power conversion efficiency (PCE) of 13% compared to the PCE of 10.9% for the OPV device with the PFN-Br interlayer. Various spectroscopic and electrical characterisation analyses of ETL materials and OPV device performance revealed that the PDIAO interlayer significantly reduces the work function of the active layer by forming interface dipole and enhanced charge transport for efficient electron extraction. These results suggest that tri(oxyethylene)-functionalised PDI derivatives are promising ETL materials for efficient electron extraction in OPV devices.