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The limited exciton lifetime (τ, generally D ) of organic semiconductors, which is the bottleneck issue impeding the further improvement of power conversion efficiencies (PCEs) for organic solar cells (OSCs). However, efficient strategies to prolong intrinsic τ are rare and vague. Herein, we propose a facile method to efficiently reduce vibrational frequency of molecular skeleton and suppress exciton-vibration coupling to decrease non-radiative decay rate and thus prolong τ via deuterating nonfullerene acceptors. The τ remarkably increases from 0.90 ns (non-deuterated L8-BO) to 1.35 ns (deuterated L8-BO-D), which is the record for organic photovoltaic materials. Besides, the inhibited molecular vibration improves molecular planarity of L8-BO-D for enhanced exciton diffusion coefficient. Consequently, the LD increases from 7.9 nm (L8-BO) to 10.7 nm (L8-BO-D). The prolonged LD of L8-BO-D enables PM6 : L8-BO-D-based bulk heterojunction OSCs to acquire higher PCEs of 18.5 % with more efficient exciton dissociation and weaker charge carrier recombination than PM6 : L8-BO-based counterparts. Moreover, benefiting from the prolonged LD , D18/L8-BO-D-based pseudo-planar heterojunction OSCs achieve an impressive PCE of 19.3 %, which is among the highest values. This work provides an efficient strategy to increase the τ and thus LD of organic semiconductors, boosting PCEs of OSCs.
Zhu et al. (Fri,) studied this question.