Ambient‐Printed Methylammonium‐Free Perovskite Solar Cells Enabled by Multiple Molecular Interactions

A 2-thiazole formamidine hydrochloride additive possessing multiple interactions with perovskite components can synchronously promote crystallization and passivate stacking defects of MA-free perovskites during ambient printing. The film shows large crystalline grains and reduced defects with stable photoactive α-phase perovskite, and endows an unencapsulated device with a high efficiency of 23.72% and 95% efficiency retention after 2088 h in air.

Abstract

The ambient printing of high-performance and stable perovskite solar cells (PSCs) is crucial for enabling low-cost and energy-efficient industrial fabrication. However, producing high-quality perovskite films via ambient printing remains challenging due to direct exposure to air, which easily induces additional stacking defects and triggers perovskite degradation compared to films fabricated by traditional spin-coating under inert conditions. Here, a multiple molecular interaction strategy is introduced to address this challenge by incorporating a 2-thiazole formamidine hydrochloride (TC) additive, effectively suppressing defect formation during ambient printing. The specific interactions between TC and precursor components, i.e., multiple hydrogen bonds and coordination interactions, could promote the crystallization of α-phase perovskites and reduce cation and anion vacancies simultaneously when drying in air. These endows high-quality ambient-printed perovskite films with large crystalline grains with eliminated nanovoids and low trap-densities, which improve charge carrier dynamics and prevent perovskite decomposition and hydration under thermal/humidity stress during long-term annealing/ambient storage. The unencapsulated PSCs show a high efficiency of 23.72% with good stability, i.e., realizing 92% and 95% efficiency retention after 672 h of annealing at 85 °C in a N₂ atmosphere and after 2088 h of storage in ambient air.