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A new fused‐ring electron acceptor FOIC1 is designed and synthesized. FOIC1 exhibits intense absorption in the range of 600–1000 nm, the highest occupied molecular orbital (HOMO)/the lowest unoccupied molecular orbital (LUMO) energy levels of −5.39/−3.99 eV, and electron mobility of 1.8 × 10 −3 cm 2 V −1 s −1 . Organic solar cells based on sequentially processed heterojunction (SHJ) with an unusual inverted structure are fabricated. Through sequentially spin‐coating polymer donor PTB7‐Th as the bottom layer and acceptor FOIC1 as the top layer, a better vertical phase distribution is formed in this SHJ compared with that in traditional bulk heterojunction (BHJ). In the upper‐half part, a more balanced donor/acceptor distribution is beneficial for exciton dissociation. At the bottom interface, more FOIC1 accumulation is beneficial for exciton generation and charge transport. Overall, the SHJ cells exhibit power conversion efficiency as high as 12.0%, higher than that of the BHJ counterpart (11.0%).
Xue et al. (Fri,) studied this question.