Fullerene-embedded porphyrin metallacages as photoactive additives for stable binary organic solar cells with a certified efficiency of 20.2%

Boosting both power-conversion-efficiency (PCE) and stability is crucial for the practical applications of organic solar cells (OSCs). Here, we synergistically improve the PCE and stability of OSCs using fullerene-embedded porphyrin metallacages (MC4⊃C60 and MC4⊃C70) as photoactive additives. Compared to the fullerene-free porphyrin metallacage (MC4) and MC4⊃C60, MC4⊃C70 exhibits superior photo-responsive activity, multistage crystallization behavior, and extraordinary non-covalent interactions with both the donor (PM6) and the acceptor (eC9-4ClO). Therefore, the MC4⊃C70-treated active layer attains improved photon harvesting capability and optimized blend morphology with ideal crystallinity, intermolecular π–π stacking, and phase separation, eventually diminishing trap density, facilitating exciton generation and dissociation, improving charge collection, and limiting charge recombination. As a result, the MC4⊃C70-treated OSCs achieve a higher PCE of 20.42% compared to those of metallacage-free (19.88%), MC4-treated (19.16%), and MC4⊃C60-treated (20.09%) OSCs. Notably, the champion OSCs achieve a certified PCE of 20.20%, ranking among the highest certified values reported for binary OSCs. Impressively, the MC4⊃C70-treated devices also offer superior long-term operation stability with an ∼90% retention of the initial PCE under maximum-power-point tracking for 500 h. This work opens a new avenue for using fullerene-embedded porphyrin metallacages as photoactive additives to manipulate the optoelectronic and morphological properties for realizing efficient and stable OSCs.