Vapor deposition of perovskite solar cells (PSCs) has attracted considerable interest for its dry processing characteristics. However, a two-step sequential vapor deposition method suffers from ineffective conversion of PbI₂ to perovskite with reasons still unclear. In this report, we carefully investigated the crystallization orientation of PbI₂ films deposited by physical vapor deposition via synchrotron grazing-incidence wide-angle X-ray scattering (GIWAXS) and observed an asymmetric scattering pattern with respect to the q_z-axis. The observed oriented morphology and texture hinder the diffusion of MAI molecules in the PbI₂ films synthesized by vapor deposition, resulting in over 15% PbI₂ remaining at the buried interface after reaction with MAI vapor. As a result, the MAPbI₃ synthesized in this way was also highly oriented, especially in the surface layers. Surface fumigation (SF) step was introduced to decrease the orientational anisotropy of PbI₂, which successfully breaks the diffusion barriers of MAI molecules by forming a complex layer on the PbI₂ surface with polar solvent vapors, like dimethyl sulfoxide or 1,3-dimethyl-2-imidazolidinone. We infer that the SF treatment changes the vapor–solid reaction mechanism from reaction–crystallization to dissolution–recrystallization, which largely promotes the conversion of PbI₂ to perovskite. Defects were reduced in perovskite synthesized in this way, and a p-i-n device with 19.56% efficiency was fabricated, which is among the highest efficiencies reported for sequential-vapor-deposited PSCs. Notably, this method enables the fabrication of conformal perovskite layers on uneven substrates. An exemplary PSC showing efficiency of 8.93% was fabricated on a precurved substrate. We believe that the method is applicable to the fabrication of tandem or curved PSCs that are compatible with wearable or building/autocar-integrated photovoltaics in the future.

中文翻译：

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用于在弯曲太阳能电池上高效合成钙钛矿的气相沉积 PbI2 薄片的表面取向消除

钙钛矿太阳能电池 (PSC) 的气相沉积因其干法加工特性而引起了人们极大的兴趣。然而，两步顺序气相沉积方法存在 PbI ₂向钙钛矿转化效率低的问题，原因尚不清楚。在本报告中，我们仔细研究了通过同步加速器掠入射广角 X 射线散射 (GIWAXS) 物理气相沉积沉积的 PbI ₂薄膜的结晶取向，并观察到相对于q _z轴的不对称散射模式。观察到的取向形态和纹理阻碍了 MAI 分子在气相沉积合成的 PbI ₂薄膜中的扩散，导致超过 15% 的 PbI ₂与 MAI 蒸气反应后留在掩埋界面。结果，以这种方式合成的MAPbI ₃也是高度取向的，尤其是在表面层中。引入表面熏蒸 (SF) 步骤以降低 PbI ₂的取向各向异性，通过在 PbI ₂表面上形成复杂层与极性溶剂蒸气（如二甲基亚砜或 1,3-二甲基）成功地打破了 MAI 分子的扩散障碍-2-咪唑烷酮。我们推断SF处理将气固反应机制从反应-结晶转变为溶解-重结晶，这在很大程度上促进了PbI ₂的转化到钙钛矿。以这种方式合成的钙钛矿中的缺陷减少了，并且制造了效率为 19.56% 的 pin 器件，这是顺序气相沉积 PSC 报告的最高效率之一。值得注意的是，这种方法能够在不平坦的基板上制造共形钙钛矿层。在预弯曲基板上制造了显示 8.93% 效率的示例性 PSC。我们相信该方法适用于未来与可穿戴或建筑/汽车集成光伏兼容的串联或弯曲 PSC 的制造。