Morphological optimization by rational matching of the donor and acceptor boosts the efficiency of alkylsilyl fused ring-based polymer solar cells

Abstract

With the development of non-fullerene organic solar cells, more and more conductive materials are available for bulk-heterojunction (BHJ) active layers. Matching of the two materials in all aspects, including energy alignment, absorption complementation, BHJ morphology etc., is very critical to obtain a high performance device. In this work, three analogues of ITIC, ITIC-F and ITIC-Th1 with different end-capping groups or side-chains were selected as non-fullerene acceptors (NFAs) for an alkylsilyl functionalized copolymer donor (PBDS-T), to reveal the basic matching principle of the donor and acceptor for optimizing the active layer morphology. We found that the interaction between the donor and acceptor, the crystallinity of each component and the difference in the surface tensions greatly impact the morphology of blend films and device performance. Such a significant change can be realized by a subtle variation of the NFA structure. As a result, the power conversion efficiency (PCE) is boosted from 10.72% to 12.04%, together with a dramatically improved fill factor (FF) of 60% for PBDS-T:ITIC, 66% for PBDS-T:ITIC-F and 70% for PBDS-T:ITIC-Th1, respectively. Note that the PCE of 12.04% is one of the best values for the devices based on alkylsilyl functionalized copolymers reported so far.