Organic-inorganic hybrid halide perovskite materials have been used in optoelectronic applications, including photodetectors, X-ray imaging, lasing, photocatalysis, lightemitting diodes, and so on. [1][2][3][4][5] Owing to their high optical absorption coefficient, low exciton binding energy, long charge carrier diffusion lengths, high photoluminescence (PL) quantum yield, suitable bandgap, and energy level, perovskite solar cells (PSCs) are emerging as promising candidates for the next-generation thin-film solar cells. [6][7][8][9][10][11] By optimizing the perovskite compositions, device structures, and deposition methods, power conversion efficiency (PCE) of PSCs has been dramatically increased from 3.8% in 2009 to the latest certified value of 25.2%, approaching the champion efficiency of the industry silicon solar cells. [12][13][14][15][16][17] The traditional lowtemperature solution-processing and fast crystallization method are widely used in synthesis of perovskite films, which inevitably introduce a large amount of defects into perovskite bulk and perovskite-transport layer interfaces (PTLIs). [18,19] Herein, PTLIs refer to the interfaces of both electron transport layer (ETL)/perovskite and perovskite/hole transport layer (HTL). It is well known that the defects can act as charge recombination centers to induce severe energy loss, thereby reducing the device efficiency. [18] Meanwhile, these trap states create conditions for the infiltration of moisture and oxygen into perovskite layer and subsequently seriously decrease the device stability. [20][21][22] Moreover, several recent studies show that defects mainly present at the PTLIs (called interface defects), which are strongly associated with the energy level alignment, charge dynamics, photocurrent hysteresis, and the long-term operational stability. [23][24][25] Therefore, it is imperative to seek an effective way to reduce the defects, especially at the PTLIs, for achieving the high-performance PSCs. Additive engineering [26][27][28][29][30][31][32][33][34] and interface engineering [35][36][37][38][39][40][41] have been regarded as effective strategies to reduce the defect density in PSCs, such as incorporating Phenyl-C61-butyric acid methyl ester (PCBM) [29] into perovskite layer to effectively passivate the defects and minimize the photocurrent hysteresis, inserting self-assembled monolayer of organic molecules with functional groups [36,37] into perovskite/ETL interface to suppress defects Defects, inevitably produced within bulk and at perovskite-transport layer interfaces (PTLIs), are detrimental to power conversion efficiency (PCE) and stability of perovskite solar cells (PSCs). It is demonstrated that a crosslinkable organic small molecule thioctic acid (TA), which can simultaneously be chemically anchored to the surface of TiO 2 and methylammonium lead iodide (MAPbI 3 ) through coordination effects and then in situ crosslinked to form a robust continuous polymer (Poly(TA)) network after thermal treatment, can be introduced into PSCs as a ...
