Material perceptions and advances in molecular heteroacenes for organic solar cells

The development of A-D-A type heteroacenes for bulk-heterojunction solar cells has gained immense interest in the last 5-6 years due to their synthetic accessibility via new molecular design, facile functionalization, tunable optoelectronic properties, cost-effective device fabrication and high efficiencies. Specifically, they have reached power conversion efficiencies (PCEs) up to 18% as electron acceptors, demonstrating their effectiveness in replacing fullerene derivatives in OSCs. This review explores the important aspects of the structural modifications of A-D-A-type heteroacenes and their application in high performance binary, ternary and tandem OSCs. The modulation of functional groups and their influence on the frontier orbital tuning, blend morphology, and charge transport properties have been comprehensively discussed as a tool for correlating molecular structures and properties with device performance beneficial for new material design. Finally, their applications and prospects in semitransparent OSCs are discussed as potential for future technology.