Optimization of active layers for efficient binary organic solar cells

Abstract

The photovoltaic performance of organic solar cells (OSCs) is closely related to the active layer and its microstructure. Therefore, it is essential to coordinately control the preparation process parameters from multiple perspectives to optimize the morphology and improve the device's photovoltaic performance. Based on the classical and efficient PM6:L8-BO active system, this paper systematically studies the effects of annealing temperature, film thickness, solvent additives, and other factors on the film microstructure, exciton generation and dissociation, charge transport, phase separation, and light absorption. The results show that an annealing temperature of 90 °C and the solvent additive diiodooctane (DIO) maximize the optimization of the micromorphology of the active layer. Finally, a champion conversion efficiency (PCE) of 18.33% was achieved for binary OSCs, under the condition of an active layer thickness of 100 nm, with an open-circuit voltage (V_oc) of 0.881 V, a short-circuit current density (J_sc) of 26.56 mA cm⁻² and a fill factor (FF) of 78.33%.