Local Structure-Induced Selective Interactions Enables High-Performance and Burn-in-Free Organic Photovoltaics

Oligomeric acceptors (OAs) have attracted considerable attention in the organic photovoltaics (OPV) field owing to their capacity in balancing the merits from both monomeric and polymeric acceptors. A delicate control over the distortion between blocks of OAs usually determines the performance and stability of relevant OPV devices. However, it imposes great complexity to realize a controllable degree of distortion by tuning the skeleton of blocks and the position of linker between blocks. Herein, we developed a facile strategy to rationally control the geometry distortion of OAs via a straightforward substitution of alkoxy side-chains on their blocks. This helps elucidate the integrated influences of molecular distortion and non-bonded contacts on the selective interactions between OA molecules and between OA and host acceptor in ternary blend. We demonstrate the alkoxy-OA molecules having stronger self-interactions would mitigate their interactions with host acceptor, therefore alleviating the kinetic diffusion and excessive aggregation of total acceptors. Combining with a composite-interlayer strategy by introducing a phenyl-substituted self-assembled monolayer to enhance the doping with polyoxometalate, an impressive efficiency of 20.1% is achieved accompanied by a negligible burn-in loss against physical aging. This study demonstrates the validation of tuning of selective interactions towards high-performance and burn-in-free OPV.