Abstract The instability of emerging perovskite solar cells at moisture (humidity) exposure is now the main target of many research groups. The moisture instability impedes the up-scaling of the solution processing perovskite solar cells for large production lines. Analyzing the crystallinity of perovskite film can reveal the sensitivity against humidity at air exposure under light and the recovery dynamic at dark conditions. In this paper, X-ray diffraction has been deployed as a reliable characterization method to detect the film crystallinity and defect formation in perovskite films. We prepared Perovskite solar cells with reduced graphene oxide as the hole transporting layer aiming to protect the perovskite layer from direct exposure to air oxygen and decomposition. Graphene has excellent heat conductivity and will accelerate the heat dissipation and light-induced degradation. It can also reduce the PbI2 defective layer formation on the perovskite surface. We have stressed the fabricated cell under light at air exposure for 30, and 45 days to track the degradation rate and then rested them in dark for 45 days to recover the performance and film crystallinity. The results were interesting: the grain size of perovskite layer reduced and the defect layer became thicker under the light of 30 and 45 days. Then a reverse phenomenon occurs at dark rest for 45 days and the grain size recovers slightly whereas the defect layer shrinks somewhat. We also observe peak (200) related to rGO layer which vanishes after 45 days and only a single peak (101) remains and becomes stronger after 45 days’ dark rest. The lattice constants of the films were calculated and the phase recovery was analyzed. The dynamic crystallinity is an additional instability source for perovskite photovoltaics.

中文翻译：

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石墨烯接触钙钛矿太阳能电池的 X 射线衍射用于在暗静止时进行水分降解和恢复

摘要 新兴钙钛矿太阳能电池在湿气（湿度）暴露下的不稳定性现在是许多研究小组的主要目标。水分不稳定性阻碍了大型生产线的溶液加工钙钛矿太阳能电池的规模化。分析钙钛矿薄膜的结晶度可以揭示光照下空气暴露对湿度的敏感性和黑暗条件下的恢复动态。在本文中，X 射线衍射已被用作一种可靠的表征方法来检测钙钛矿薄膜中的薄膜结晶度和缺陷形成。我们制备了具有还原氧化石墨烯作为空穴传输层的钙钛矿太阳能电池，旨在保护钙钛矿层免受直接暴露于空气中的氧气和分解。石墨烯具有优异的导热性，会加速散热和光诱导降解。它还可以减少钙钛矿表面上 PbI2 缺陷层的形成。我们已将制造的电池在暴露于空气的光线下加压 30 天和 45 天以跟踪降解率，然后将它们在黑暗中静置 45 天以恢复性能和薄膜结晶度。结果很有趣：在 30 天和 45 天的光照下，钙钛矿层的晶粒尺寸减小，缺陷层变厚。然后在暗静置 45 天时出现相反的现象，晶粒尺寸略有恢复，而缺陷层有所收缩。我们还观察到与 rGO 层相关的峰 (200)，该峰在 45 天后消失，只有一个峰 (101) 保留并在 45 天的暗休息后变得更强。计算薄膜的晶格常数并分析相恢复。动态结晶度是钙钛矿光伏的额外不稳定源。