解释钙钛矿材料的时间分辨光致发光,Physical Chemistry Chemical Physics

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解释钙钛矿材料的时间分辨光致发光
Physical Chemistry Chemical Physics ( IF 2.9 ) Pub Date : 2020-11-23 , DOI: 10.1039/d0cp04950f
Emmanuel V. Péan _{1,

2,

3,

4,

5} , Stoichko Dimitrov _{6,

7,

8,

9} , Catherine S. De Castro _{10,

11,

12} , Matthew L. Davies _{1,

2,

3,

4,

5}

Affiliation

时间分辨光致发光（TRPL）光谱技术是研究半导体和分子系统中激发的载流子复合的强大技术。分析许多分子系统的TRPL衰减（例如，分子和有机材料）通常是相当简单的，并且可以装配指数函数以提取速率常数。由于卤化钙钛矿材料中电荷载流子的非激子性质，以及其带隙中存在局部陷阱态，因此这些材料的TRPL解释起来要复杂得多。在这里，我们讨论文献中使用的两个模型来模拟钙钛矿中的载流子复合和TRPL。这些模型考虑了直接的电子-空穴重组的双分子性质，但是在其对陷阱介导的重组的处理上有所不同，一个模型将陷阱描述为单分子过程，而将另一个模型描述为自由载体与可用陷阱态之间的双分子过程。相比下，钙钛矿TRPL衰减曲线的经典分析（使用指数和）可能会导致误解。在这里，我们为有意义的卤化钙钛矿铅薄膜的测量提供了一些建议。对于两个模型，都讨论了由于连续激发脉冲之间所有光激发载流子的不完全减少而导致的注量依赖性以及电荷载流子累积。

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Interpreting time-resolved photoluminescence of perovskite materials

Time-resolved photoluminescence (TRPL) spectroscopy is a powerful technique to investigate excited charge carrier recombinations in semiconductors and molecular systems. The analysis of the TRPL decays of many molecular systems (e.g. molecules and organic materials) is usually fairly straightfoward and can be fitted with an exponential function allowing extraction of the rate constants. Due to the non-excitonic nature of charge carriers in lead halide perovskite materials coupled with the presence of localised trap states in their band-gap, the TRPL of these materials is much more complicated to interpret. Here we discuss two models used in the literature to simulate charge carrier recombinations and TRPL in perovskites. These models consider the bimolecular nature of direct electron–hole recombination but differ in their treatment of trap-mediated recombination with one model describing trapping as a monomolecular process whereas the other as a bimolecular process between free carriers and the available trap states. In comparison, the classical analysis of perovskite TRPL decay curves (using a sum of exponentials) can lead to misinterpretation. Here we offer some recommendations for meaningful measurements of lead halide perovskite thin-films. The fluence dependence as well as charge carrier accumulation due to incomplete depopulation of all photoexcited carriers between consecutive excitation pulses are discussed for both models.

更新日期：2020-12-10

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