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.