Fullerene-Embedded Porphyrin Metallacages as Photoactive Additives for Stable Binary Organic Solar Cells with a Certificated Efficiency of 20.2%

Boosting both power-conversion-efficiency (PCE) and stability are crucial for the practical applications of organic solar cells (OSCs). Here, we synergistically improve PCE and stability of OSCs using fullerene-embedded porphyrin metallacages (MC4⊃C60 and MC4⊃C70) as photoactive additives. Compared to fullerene-free porphyrin metallacage (MC4) and MC4⊃C60, MC4⊃C70 has superior photo-responsive activity, multistage crystallization, and extraordinary non-covalent interactions with both donor (PM6) and acceptor (eC9-4ClO). Therefore, the MC4⊃C70-treated active layer obtains 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 provide a higher PCE of 20.42% compared to those metallacage-free (19.88%), MC4 (19.16%), and MC4⊃C60 (20.09%) treated OSCs. Notably, the champion OSCs achieve a certified PCE of 20.20%, ranking among the highest certified values for binary OSCs. Impressively, the MC4⊃C70-treated devices also offer superior long-term operation stability with a ~90% retention of the initial PCE under maximum-power-point tracking for 500 h. This work opens a new avenue of using fullerene-embedded porphyrin metallacages as photoactive additives to manipulate the optoelectronic and morphological properties for realizing efficient and stable OSCs.