Quantifying Voc loss induced by alkyl pendants of acceptors in organic solar cells

Abstract

In the organic photovoltaic community, extensive efforts have been made in proposing resolutions for depressing V_oc loss related to the molecular structures and optoelectronic properties of materials in bulk heterojunctions. Focusing on understanding the origin of aggregation-induced V_oc loss and exploring the generality for material design, we used non-fullerene acceptors with various alkyl pendants in bulk heterojunctions and characterized the optoelectronic properties. As the alkyl pendants became longer from IT-4Cl-C6 to IT-4Cl-C10, the photovoltaic devices exhibited depressed V_oc losses and improved power conversion efficiencies. This work expounds the structure activity relationship of alkyl pendant-dependent photovoltaic properties, suggesting a convincing guideline for non-fullerene acceptor design.