Prolonging charge carrier lifetime via reinforcing molecular stacking for high-efficiency organic solar cells

Limited charge carrier lifetime (τ) leads to the short charge carrier diffusion length (L_D) and thus impedes the improvement of power conversion efficiencies (PCEs) of organic solar cells (OSCs). Herein, anthracene (AN) as the additive is introduced into classical donor: acceptor pairs to increase the τ. Introducing AN efficiently enhances the crystallinity of the PM6:BTP-eC9+ blend film to reduce the trap density and increase the τ to 1.48 µs, achieving the prolonged L_D. The prolonged L_D enables the PM6:BTP-eC9+ blend film to gain weaker charge carrier recombination, reduced leakage current, and shorter charge carrier extraction time in devices, compared with PM6: BTP-eC9 counterparts. Therefore, PM6:BTP-eC9+ based OSCs achieve higher PCEs of 18.41%±0.16% than PM6:BTP-eC9 based ones (17.08%±0.11%). Moreover, the PM6:L8-BO+ based OSC presents an impressive PCE of 19.14%. It demonstrates that introducing AN is an efficient method to increase the τ for prolonged L_D, boosting PCEs of OSCs.