Efficient organic solar cells by modulating photoactive layer morphology with halogen-free additives

Optimizing the morphology of the photoactive layer by additives strategy is one of the successful methods for increasing efficiency in organic solar cells (OSCs). In this work, a halogen-free solvent additive, methoxy methyl phenyl sulfide (MMPS) added to the PTB7-Th:PC71BM-based system to improve the optoelectronic property for OSCs by modulating the phase separation and crystallinity in the photoactive layer. It is found that the addition of MMPS could well modulate the aggregation and diffusion of donor and acceptor to form an excellent bicontinuous interpenetrating network, which improved exciton dissociation enhanced charge transport and significantly inhibited charge recombination. Consequently, the PCE of device based on the PTB7-Th:PC71BM blend with 3% MMPS is 9.24%, which is a 92.5% efficiency improvement compared to the device without additives. These results indicate that our work effectively optimizes the performance parameters of devices, providing new ideas for the preparation of OSCs on a large scale and industrialization.