High-Efficiency Organic Solar Cells with Reduced Nonradiative Voltage Loss Enabled by a Highly Emissive Narrow Bandgap Fused Ring Acceptor

Increasing the photoluminescence quantum yield (PLQY) of narrow bandgap acceptors is of critical importance to suppress the nonradiative voltage loss (Delta V-nr) in organic solar cells (OSCs). Herein, two acceptors, SM16 and SM16-R, with an identical backbone but different terminal groups (norbornenyl modified 1,1-dicyanomethylene-3-indanone and dimethyl substituted 1,1-dicyanomethylene-3-indanone) are designed and synthesized. Compared with SM16-R, SM16 displays better solubility, higher PLQY, and more favorable nanomorphology when blended with polymer donor PBDB-T. PBDB-T:SM16-based OSCs yield a Delta V-nr as low as 0.145 V. Using SM16 as the third component, a high power conversion efficiency of 17.1% is achieved in the ternary OSCs based on PBDB-T:Y14:SM16, considerably higher than that of the binary devices based on PBDB-T:Y14 or PBDB-T:SM16. These results highlight that enhancing the PLQY of low bandgap acceptor via terminal group engineering strategy is highly effective to reduce Delta V-nr of OSCs.

Automated summary

In this study, two acceptors with different terminal groups but identical backbones were designed to enhance the PLQY of low bandgap acceptors. The results showed that improving the PLQY through terminal group engineering strategy effectively reduces nonradiative voltage loss in OSCs. A high power conversion efficiency of 17.1% was achieved in ternary OSCs based on the third component, SM16.