Interfacial Hydrogen Bonding for Efficient and Robust Flexible Tin Perovskite Solar Cells

ABSTRACT Flexible tin perovskite solar cells (F‐TPSCs) have attracted substantial attention owing to their high theoretical efficiency, eco‐friendliness, and promising applications in wearable electronics and the internet of things. However, the inferior quality of perovskite buried interfaces caused by low interfacial adhesion and large deformation of plastic substrates has seriously impaired the performance of F‐TPSCs. Here, a biocompatible functional material, 1‐chloro‐1‐deoxy‐D‐fructose (1‐CDF), has been introduced into the poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) hole‐transporting layer, which enables hydrogen‐bonding interactions between PEDOT:PSS and both the underlying ITO and the top perovskite layer, thus significantly enhancing the interfacial adhesion. It can also regulate the crystallization dynamics of the perovskite, resulting in the growth of pinhole‐free perovskite film with high crystallinity and homogeneous bottom contact. Besides, the incorperation of 1‐CDF leads to conformation changes of the PEDOT:PSS, rendering higher conductivity and more matched energy level alignment with perovskites. The power conversion efficiencies (PCEs) of 15.56% (14.67% certified) and 11.06% are reached for F‐TPSCs with active areas of 0.049 cm 2 and 1 cm 2 , respectively. In addition, the F‐TPSC obtains an unprecedented PCE of 22.21% under 1000 lux indoor light illumination. The unencapsulated devices also exhibit excellent stability.