Morphology optimization of photoactive layers in organic solar cells

Abstract Organic solar cells (OSCs) have unique advantages of light weight, low‐cost solution processing, and capability to be fabricated into flexible and semitransparent devices, which are widely recognized as a promising photovoltaic technology. Photoactive layers of the OSCs are composed of a blend of a p ‐type organic semiconductor as a donor (D) and an n ‐type organic semiconductor as acceptor (A). The morphology of the active layer with D/A nano‐scaled aggregation and face‐on π‐conjugated packing, and D/A interpenetrating network is crucial for achieving high photovoltaic performance of the OSCs. Therefore, great efforts have been devoted to control and optimize morphology of the active layers. This perspective focuses on the morphological control by solvent/solid processing additives and the morphology optimization by postdeposition treatment with thermal annealing and/or solvent vapor annealing, which have been extensively adopted and exhibit promising positive effect in optimizing the morphology. Representative examples are given and discussed to understand the foundation of the postdeposition treatments on tuning the morphology. Insights into the role of the postdeposition treatments and additive treatments on the morphology optimization will be beneficial to further improvement in morphology optimization for practical organic photovoltaic application.