The properties of perovskite/naphtho[2,3-a]pyrene (NaPy) upconversion devices are investigated by a combination of atomic force microscopy and photoluminescence mapping to understand the role of microscopic heterogeneity in the ensemble device properties. The results emphasize strong microscopic inhomogeneity across the perovskite/NaPy upconversion device due to local formation of NaPy microcrystals. NaPy shows emission from three distinct states in the solid state: S₁′ emission at 520 nm, excimer emission at 560 nm, and S₁″ emission at 620 nm. Clear spatial differences in the emission spectrum under 405 nm excitation are found, highlighting that there is a strong microcrystal-to-microcrystal variation in the optical properties─emphasizing a need for multimodal measurements. Our results indicate that microcrystals with strong emission from the strongly coupled low-energy state S₁″ (J-dimer) show much higher upconversion intensity than those with dominant emission from the high-energy S₁′ state (I-aggregate). Hence, our results suggest that microcrystals with strong emission from the low-energy state S₁″ act as isolated hotspots for upconversion.

中文翻译：

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微米尺度上的上转换：局部异质性的影响


通过原子力显微镜和光致发光映射相结合研究钙钛矿/萘氧[2,3-a]芘 （NaPy） 上转换器件的特性，以了解微观异质性在集成器件特性中的作用。结果强调了由于 NaPy 微晶的局部形成，钙钛矿/NaPy 上转换器件具有很强的微观不均匀性。NaPy 显示固态中三种不同状态的发射：520 nm 处的 S₁' 发射、560 nm 处的准分子发射和 620 nm 处的 S₁“ 发射。在 405 nm 激发下，发射光谱存在明显的空间差异，突出表明光学特性存在强烈的微晶间差异，强调需要进行多模态测量。我们的结果表明，从强耦合低能量态 S₁“ （J-二聚体） 发出强发射的微晶比从高能 S₁' 状态 （I-聚集体） 具有主要发射的微晶显示出更高的上转换强度。因此，我们的结果表明，从低能态 S₁“ 发出强发射的微晶充当上转换的孤立热点。