Interfaces are essential for solar cell performance since they govern charge separation and transport. Using quantum dynamics simulation, we demonstrate that at interfaces, common defects that are benign on their own, iodine vacancy in CH₃NH₃PbI₃ (V_I) and oxygen vacancy in TiO₂ (V_O), are responsible synergistically for poor stability and charge losses. V_O promotes V_I diffusion and accelerates iodine migration. A midgap trap state appears, inhibiting charge transport and accelerating charge recombination by an order of magnitude. Strong structural distortions strengthen electron-vibrational interactions and activate high-frequency TiO₂ phonons. Because of the widely reported high defect-tolerance of lead-halide perovskites, the synergistic detrimental influence of perovskite defects with defects in other materials is often overlooked. The interfacial defect pairing could be a major reason for poor stability and charge losses in perovskite solar cells. The results suggest that either a high-quality perovskite or high-quality charge extraction layer may be sufficient to achieve high performance.

中文翻译：

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TiO2/CH3NH3PbI3 界面处的有害缺陷协同性：稳定性降低、离子扩散增强、电荷寿命和传输减少


接口对于太阳能电池的性能至关重要，因为它们控制着电荷分离和传输。利用量子动力学模拟，我们证明在界面处，自身是良性的常见缺陷，CH₃NH₃PbI₃ （V） 中的碘空位和 TiO₂ （V_O） 中的氧空位，协同导致稳定性差和电荷损失。V_O 促进 V 扩散并加速碘迁移。出现中隙陷阱状态，抑制电荷传输并将电荷复合加速一个数量级。强烈的结构扭曲增强了电子-振动相互作用并激活高频 TiO₂ 声子。由于氢化铅钙钛矿的高缺陷容差被广泛报道，钙钛矿缺陷与其他材料缺陷的协同不利影响经常被忽视。界面缺陷配对可能是钙钛矿太阳能电池稳定性差和电荷损失的主要原因。结果表明，高质量的钙钛矿或高质量的电荷提取层可能足以实现高性能。