Rational Mutual Interactions in Ternary Systems Enable High-Performance Organic Solar Cells

Ternary organic solar cells (TOSCs) offer a facile and efficient approach to increase the power conversion efficiencies (PCEs). However, the critical roles that guest components play in complicated ternary systems remain poorly understood. Herein, two acceptors named LA1 and LA9 with differing crystallinity are investigated. The overly crystalline LA9 induces large self-aggregates in PM6:LA9 binary system, resulting in a lower PCE (13.12%) compared to PM6:LA1 device (13.89%). Encouragingly, both acceptors are verified as efficient guest candidates into the host binary PM6:NCBDT-4Cl (PCE = 13.48%) and afford markedly improved PCEs up to 15.39% and 15.75% in LA1 and LA9 ternary devices, respectively. Interestingly, the higher crystallinity LA9 reveals smaller interaction energies with both the host acceptor and donor PM6. Compared to LA1, the appropriate mutual interactions in the LA9 ternary system not only induces the orderly crystallinity of PM6 but also better compatibility with the host acceptor, generating further optimized molecular orientations and ternary morphology. Therefore, enhanced charge transport and minimized recombination loss are detected in LA9 ternary devices, affording the most competitive performance among Y6-sbsent TOSCs. This work suggests that complicated intermolecular interactions should be seriously considered when fabricating state-of-the-art multiple components OSCs.

Automated summary

This study investigates the roles of two acceptors with different crystallinity, LA1 and LA9, in ternary organic solar cells. It is found that LA9, with higher crystallinity, tends to form large self-aggregates, leading to decreased device performance compared to LA1. Both acceptors show improved device performance when incorporated into the binary host compound, with the appropriate interactions of LA9 inducing ordered crystallinity and better compatibility with the host acceptor.