Abstract The morphology of hybrid perovskite thin films plays a crucial role for their photophysical properties. However, the underlying mechanisms are still unclear. To gain further insight into this phenomenon, methylammonium lead tribromide films of different morphology were investigated using photoluminescence spectroscopy. Photostability measurements demonstrate three mechanisms: (A) reversible degradation of the photoluminescence, depending positively on the grain-boundary density, which is presumably caused by photo-induced bromide vacancies, (B) enhancement of the photoluminescence intensity in the presence of oxygen and moisture and (C) destruction of the perovskite after several minutes of ultraviolet illumination with excitation power above 100 W/cm2. Both the intensity and the lifetime of the photoluminescence were significantly smaller in films with micrometer-sized crystallites compared to granular films. This is ascribed to crystals being partially isolated in the former, causing smaller diffusion lengths, whereas the carriers in the granular films can diffuse from grain to grain resulting in higher photoluminescence lifetime and intensity.

中文翻译：

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形貌对甲基铵三溴化铅薄膜光致发光性能的影响

摘要 杂化钙钛矿薄膜的形貌对其光物理性能起着至关重要的作用。然而，其潜在机制仍不清楚。为了进一步了解这种现象，使用光致发光光谱研究了不同形态的甲基铵三溴化铅薄膜。光稳定性测量表明三种机制：（A）光致发光的可逆降解，正取决于晶界密度，这可能是由光致溴化物空位引起的，（B）在氧气和水分存在下光致发光强度的增强(C) 在激发功率高于 100 W/cm2 的紫外线照射几分钟后钙钛矿的破坏。与粒状薄膜相比，具有微米级微晶的薄膜的光致发光强度和寿命都明显更小。这是由于晶体在前者中被部分隔离，导致更小的扩散长度，而颗粒膜中的载流子可以从颗粒扩散到颗粒，从而导致更高的光致发光寿命和强度。