Dimeric Acceptors Using Different Central Linkers to Manipulate Electronic and Morphological Properties

Abstract

Dimerized acceptors show promise in combining the high performance of small-molecule non-fullerene acceptors (NFAs) with the excellent stability of polymer acceptors. The central linking units that connect two acceptor molecules together have a profound impact on dimeric acceptor properties and structure-performance relationships in blended thin films. It is seen that different linkers significantly affect the electronic properties and morphology in blended thin film. The electron-donating linker elevates the absorption coefficient, affords a lower bandgap, and reduces energy loss, and thus better photovoltaic device performance. Better fibrillar morphology can be obtained. The best material DY-EDOT-based device shows a power conversion efficiency (PCE) of 18.21%, an open-circuit voltage (V_oc) of 0.924 V, a short-circuit current density (J_sc) of 25.20 mA cm⁻², a fill factor (FF) of 78.19%, which is among the highest value for dimerized acceptors. This study reveals the fundamental importance of linker units in determining the dimerized acceptor properties and provides useful strategies for developing oligomeric and polymeric acceptors, which is critical in simultaneously improving the performance and stability of organic solar cells (OSCs).