An effective strategy to improve the performance and stability of perovskite solar cells is to deposit a 2D perovskite capping layer on the 3D perovskite. However, when exposed to light, small A-site cations in 3D perovskite exchange with the bulky cations in the 2D layer and degrade the 2D/3D interface. Therefore, to achieve long-term stability in perovskite solar cells, it is important to understand the nature of the photogenerated charge carriers that cause cation migrations at the 2D/3D interface. In this work, we fabricated 2D/3D perovskite stacks on glass, ITO, ITO/PTAA, ITO/PTAA/CuI, and ITO/SnO₂. A combination of grazing incidence X-ray diffraction and steady-state and time-resolved photoluminescence studies reveals the link between the light-induced degradation and the photogenerated charge carrier dynamics. Upon illumination, the stability of the 2D layers follows this trend: ITO/PTAA/CuI ≈ ITO > ITO/PTAA > glass > ITO/SnO₂ (from stable to unstable). This trend suggests that efficiently extracting holes from the 3D layer can improve the stability of the 2D layer. We also found that 2D/3D stacks degrade faster when illuminated from the 2D side instead of the 3D side. Our studies suggest that to achieve a stable 2D/3D interface, hole accumulation in the 3D layer should be avoided, and the exciton density in the 2D layer should be reduced.

中文翻译：

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光生电荷载流子对 2D/3D 钙钛矿界面稳定性的影响


提高钙钛矿太阳能电池性能和稳定性的有效策略是在 3D 钙钛矿上沉积 2D 钙钛矿覆盖层。然而，当暴露在光线下时，3D 钙钛矿中的小 A 位阳离子与 2D 层中的大块阳离子交换并降解 2D/3D 界面。因此，为了在钙钛矿太阳能电池中实现长期稳定性，了解在 2D/3D 界面引起阳离子迁移的光生电荷载流子的性质非常重要。在这项工作中，我们在玻璃上制造了 2D/3D 钙钛矿堆栈、ITO、ITO/PTAA、ITO/PTAA/CuI 和 ITO/SnO₂。掠入射 X 射线衍射与稳态和时间分辨光致发光研究相结合，揭示了光诱导降解与光生电荷载流子动力学之间的联系。在照明时，2D 层的稳定性遵循以下趋势：ITO/PTAA/CuI ≈ ITO > ITO/PTAA > 玻璃 > ITO/SnO₂（从稳定到不稳定）。这一趋势表明，从 3D 层中有效地提取孔可以提高 2D 层的稳定性。我们还发现，当从 2D 侧而不是 3D 侧照明时，2D/3D 堆栈的退化速度更快。我们的研究表明，要获得稳定的 2D/3D 界面，应避免 3D 层中的空穴堆积，并应降低 2D 层中的激子密度。