Dual-interface engineering induced by silane coupling agents with different functional groups constructing high-performance flexible perovskite solar cells

Defect-induced charge non-radiative recombination loss at perovskite/charge transport layers (CTLs) interfaces greatly deteriorates the efficiency and stability of flexible perovskite solar cells (PSCs). Therefore, a comprehensive strategy for reducing the defect density both at perovskite/CTLs interfaces is urgently required. Herein, the 1-[3-(Trimethoxysilyl)propyl]urea (TMPU) material is adopted to improve the conductivity of SnO2 and passivate the unfavorable SnO2/perovskite interface defects. Meanwhile, the trimethoxy(3,3,3-trifluoropropyl)silane (TMFS) layer is employed at perovskite/spiro-OMeTAD interface for the sake of suppressing the surface defects of perovskite and ameliorating environmental stability of the perovskite. Such a dual-interface engineering strategy is beneficial to significantly reduce interface defect density and unfavorable non-radiative recombination loss, thus achieving faster transport and effective collection of carriers. Consequently, the optimized flexible and rigid PSCs yield outstanding photoelectric conversion efficiency (PCE) of 20.06% and 23.11%, respectively, which are both significantly higher than the pristine devices. Notably, the target flexible device presents excellent mechanical durability and retains 91.3% of the initial PCE after 5000 bending cycles with bending radius of 10 mm.