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首页> 外文期刊>Science Advances >Origin of unusual bandgap shift and dual emission in organic-inorganic lead halide perovskites
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Origin of unusual bandgap shift and dual emission in organic-inorganic lead halide perovskites

机译：有机-无机卤化铅钙钛矿中异常带隙位移和双重发射的起源

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Emission characteristics of metal halide perovskites play a key role in the current widespread investigations into their potential uses in optoelectronics and photonics. However, a fundamental understanding of the molecular origin of the unusual blueshift of the bandgap and dual emission in perovskites is still lacking. In this direction, we investigated the extraordinary photoluminescence behavior of three representatives of this important class of photonic materials, that is, CH3NH3PbI3, CH3NH3PbBr3, and CH(NH2)2PbBr3, which emerged from our thorough studies of the effects of temperature on their bandgap and emission decay dynamics using time-integrated and time-resolved photoluminescence spectroscopy. The low-temperature (3NH3PbI3 and CH3NH3PbBr3 reveals two distinct emission peaks, whereas that of CH(NH2)2PbBr3 shows a single emission peak. Furthermore, irrespective of perovskite composition, the bandgap exhibits an unusual blueshift by raising the temperature from 15 to 300 K. Density functional theory and classical molecular dynamics simulations allow for assigning the additional photoluminescence peak to the presence of molecularly disordered orthorhombic domains and also rationalize that the unusual blueshift of the bandgap with increasing temperature is due to the stabilization of the valence band maximum. Our findings provide new insights into the salient emission properties of perovskite materials, which define their performance in solar cells and light-emitting devices.
机译：金属卤化物钙钛矿的发射特性在当前对其在光电子学和光子学中的潜在用途的广泛研究中起着关键作用。但是，仍然缺乏对钙钛矿中带隙异常蓝移和双重发射的分子起源的基本了解。在这个方向上，我们研究了这一重要光子材料的三个代表CH 3 NH 3 PbI 3 ，CH 3 NH 3 PbBr 3 和CH（NH 2 ） 2 PbBr 3 ，这是通过使用时间积分和时间分辨光致发光光谱对温度对其带隙和发射衰减动力学的深入研究而得出的。低温（3 NH 3 PbI 3 和CH 3 NH 3 PbBr 3 显示两个不同的发射峰，而CH（NH 2 ） 2 PbBr 3 的发射峰显示单个发射峰。此外，无论钙钛矿成分如何，带隙都会通过将温度从15 K升高到300 K来显示异常的蓝移。密度泛函理论和经典分子动力学模拟允许将额外的光致发光峰分配给分子无序正交晶域，并对其进行合理化处理。带隙随温度升高而发生的异常蓝移是由于价带最大值的稳定所致，我们的发现为钙钛矿材料的显着发射特性提供了新的见解，钙钛矿材料的显着发射特性决定了它们在太阳能电池和发光器件中的性能。

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