Intrinsic boundaries formed by grain stacks of randomly oriented perovskite crystallites seriously restrict charge transport in the resultant photovoltaic devices, whereas direct passivation of these defects remains unexplored, and it is desirable to modulate perovskite growth with uniform orientation. Herein, we report a simple but effective method to regulate perovskite crystallization by employing a volatile and polymerizable monomer of hydroxyethyl methacrylate (HEMA), which can simultaneously interact with both FA⁺ and Pb²⁺ via hydrogen and coordination bonding, respectively, to seed perovskite crystallization with accelerated nucleation and retarded crystal growth. Upon thermal annealing, the gradual volatilization and partial self-condensation of the HEMA drive the perovskite growth perpendicularly to the substrate, leading to largely suppressed defect states, improved crystallinity, and a reduced Young’s modulus of the perovskite film. As a result, champion efficiencies exceeding 24 and 22% with improved operational and mechanical stability of the optimized perovskite solar cells based on rigid and flexible substrates were finally achieved.

中文翻译：

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具有最小化本征边界的垂直取向钙钛矿，可实现高效光伏发电

由随机取向的钙钛矿微晶的晶粒堆叠形成的本征边界严重限制了所得光伏器件中的电荷传输，而这些缺陷的直接钝化仍未被探索，并且需要以均匀取向来调节钙钛矿生长。在此，我们报道了一种简单而有效的方法来调节钙钛矿结晶，通过使用甲基丙烯酸羟乙酯（HEMA）的挥发性和可聚合单体，该单体可以同时分别通过氢键和配位键与FA ⁺和Pb ²⁺相互作用，以形成钙钛矿晶种加速成核和延迟晶体生长的结晶。热退火后，HEMA 的逐渐挥发和部分自缩合驱动钙钛矿垂直于基底生长，从而大大抑制了钙钛矿薄膜的缺陷态、提高了结晶度并降低了杨氏模量。最终，基于刚性和柔性基板的优化钙钛矿太阳能电池的效率分别超过 24% 和 22%，并提高了运行和机械稳定性。