Antisolvent seeding of self-assembled monolayers for flexible monolithic perovskite/Cu(In,Ga)Se2 tandem solar cells

Abstract

Flexible perovskite/copper indium gallium selenide (CIGS) tandem solar cells hold great promise for lightweight, high-efficiency applications, yet achieving high-quality perovskite top cells on the rough surfaces of flexible CIGS bottom cells remains challenging. Accordingly, we developed an antisolvent-seeding strategy that decouples self-assembly monolayers (SAMs) adsorption from dissolution, while integrating perovskite seeding. A high-polarity solvent prevents SAMs clustering during dissolution, while a low-polarity antisolvent promotes high-density SAMs formation during adsorption. Additionally, a pre-mixed seed layer further improves perovskite wettability, crystallinity and adhesion. These advancements enable the fabrication of a 1.09-cm2 flexible monolithic perovskite/CIGS tandem with a stabilized efficiency of 24.6% (certified 23.8%), comparable to the best-performing rigid perovskite/CIGS tandems and representing one of the highest efficiencies among flexible thin-film solar cells. The flexible devices also demonstrate excellent durability, retaining over 90% of initial performance after 320 h of operation and 3,000 bending cycles at a 1-cm radius. The uneven surfaces of copper indium gallium selenide (CIGS) solar cells pose challenges for depositing the upper layers in flexible perovskite/CIGS tandem solar cells. Ying et al. tackle this issue using an antisolvent and seeding strategy, resulting in a certified efficiency of 23.8%.