Enriching conductive capping by alkaline treatment of perovskite quantum dots towards certified 18.3%-efficient solar cells

Perovskite quantum dots (PQD) hold great promise for next-generation photovoltaics. However, neat ester antisolvents hydrolyze inefficiently into target ligands under ambient conditions, compromising the formation of integral conductive capping on PQD surfaces. Herein, we construct alkaline environments, which facilitate the rapid substitution of pristine insulating oleate ligands with up to twice the conventional amount of hydrolyzed conductive counterparts. Theoretical calculations reveal that this environment renders ester hydrolysis thermodynamically spontaneous and lowers reaction activation energy by approximately 9-fold. Through tailoring potassium hydroxide coupled with methyl benzoate antisolvent for interlayer rinsing of PQD solids, the assembled light-absorbing layers exhibit fewer trap-states, homogeneous orientations, and minimal particle agglomerations. Consequently, the fabricated solar cells (0.036 cm²) achieve a certified efficiency of 18.3%, the highest value among published PQD solar cell reports, alongside a steady-state efficiency of 17.85% and an average efficiency of 17.68% over 20 devices. Moreover, the alkaline treatment is broadly compatible with diverse solid-state treatments and PQD compositions, demonstrating universality in modulating PQD surface chemistry.