45.73 W/g Ultra-flexible Perovskite Solar Cells Enabled with Benzyl Benzylcarbamate Additives

Ultra-flexible perovskite solar cells (UF-PSCs) hold immense promise for wearable and aerospace applications, yet their development is limited by the intrinsic brittleness of perovskite films, which severely limits their mechanical durability under extreme bending on ultrathin substrates. To address this challenge, we develop a bulk stress-releasing and lattice-stabilization strategy by introducing benzyl benzylcarbamate (BBc) as a multifunctional additive. The carbonyl group in BBc exploits its negative electrostatic potential (-36.93 kcal mol-1) to form stable coordination bonds with undercoordinated Pb2+, simultaneously passivating defects and reinforcing mechanical integrity. Concurrently, benzyl groups dissipate stress through π-π interactions and act as steric cushions. As a result, rigorous bending tests demonstrate improved mechanical durability: devices on 5- and 10-µm substrates retain over 98% and 95% of their initial PCE, respectively, after 2000 and 5000 bending cycles. Furthermore, the modified UF-PSCs retain 90% of their initial PCE after strict crumpling tests, exhibiting excellent resistance to severe mechanical deformation. In addition, the incorporation of BBc enhances crystallinity, reduces defect density, and improves charge-carrier dynamics, yielding BBc-modified UF-PSCs with a notable PCE of 20.7% and an ultra-high power-to-weight ratio of 45.73 W g-1. This work establishes a targeted chemical reinforcement strategy to develop UF-PSCs with simultaneous high efficiency and mechanical robustness.