Despite their impressive performance as a solar absorber, much remains unknown on the fundamental properties of metal halide perovskites (MHPs). Their polar nature in particular is an intense area of study, and the relative permittivity (εr) is a parameter widely used to quantify polarization over a range of different time scales. In this report, we have exploited frequency-dependent time-resolved microwave conductivity (TRMC) to study how εr values of a range of MHPs change as a function of time, upon optical illumination. Further characterization of charge carriers and polarizability are conducted by femtosecond transient absorption and stimulated Raman spectroscopy. We find that changes in εr are roughly proportional to photogenerated carrier density but decay with a shorter time constant than conductance, suggesting that the presence of charge carriers alone does not determine polarization.

中文翻译：

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光照下金属卤化物钙钛矿介电常数的时间分辨变化

尽管它们作为太阳能吸收器的性能令人印象深刻，但金属卤化物钙钛矿 (MHP) 的基本特性仍有很多未知。它们的极性性质尤其是一个研究热点，相对介电常数 (εr) 是一个广泛用于量化不同时间尺度范围内的极化的参数。在本报告中，我们利用与频率相关的时间分辨微波电导率 (TRMC) 来研究在光学照明下，一系列 MHP 的 εr 值如何随时间变化。通过飞秒瞬态吸收和受激拉曼光谱进一步表征电荷载流子和极化率。我们发现 εr 的变化大致与光生载流子密度成正比，但衰减的时间常数比电导更短，