Mechanically stable screen-printed flexible perovskite solar cells via selective self-assembled siloxane coupling agents

Owing to unique advantages of patternability and high substrate compatibility, screen-printing allows for the fabrication of flexible perovskite solar cells (f-PSCs) with designable device patterns, while the defective and fragile contact at the buried interface seriously restricted the device performance. Herein, a series of siloxane coupling agents (SCAs) with different ending groups i.e., –SH, –NH₂, and –CN were incorporated at the SnO₂/perovskite interface, which can selectively interact with MA⁺ and Pb²⁺ via hydrogen and coordination bonding, respectively. It was revealed that the selection of (3-Cyanopropyl)Triethoxysilane (CN-PTES) can regulate perovskite crystallization with accelerated nucleation and retarded crystal growth, leading to improved crystallinity with released residual lattice strain. Moreover, the incorporated CN-PTES aligned the energy structure of the underlying SnO₂ and boosted the interfacial adhesion between perovskite and SnO₂, resulting in facilitated electron extraction and enhanced interfacial fracture energy. Consequently, the first screen-printed f-PSCs with improved mechanical resistance were finally obtained.