Hot-carrier cooling and photoinduced refractive index changes in organic-inorganic lead halide perovskites.
Hot-carrier cooling and photoinduced refractive index changes in organic-inorganic lead halide perovskites.
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DOI：
10.1038/ncomms9420
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发表时间：
2015-09-25
影响因子：
16.6
通讯作者：
Deschler F
中科院分区：
文献类型：
--
作者：
Price MB;Butkus J;Jellicoe TC;Sadhanala A;Briane A;Halpert JE;Broch K;Hodgkiss JM;Friend RH;Deschler F
金属卤化物钙钛矿由于其溶液加工性和优异的半导体性能而处于光电研究的前沿。在这里，我们使用瞬态吸收光谱研究CH 3 NH3 PbI 3中的热载流子分布和量化的关键半导体参数。在带隙以上，非共振激发在100 fs内产生准热化载流子分布。在载流子冷却过程中，一个子带隙瞬态吸收信号出现在1.6 eV，这是解释的带隙重整化和热载流子分布的相互作用。在较高的激发密度下，“声子瓶颈”大大减缓了载流子冷却。这种效应表明，在这些多晶材料中，非弹性载流子-杂质或声子-杂质散射的贡献较低，这支持高电荷载流子迁移率。光致反射率的变化扭曲的瞬态吸收光谱的形状，必须包括提取物理常数。使用一个简单的能带填充模型，占这些变化，我们确定了一个小的有效质量的mr=0.14 mo，这与能带结构计算和高光伏性能。 有机-无机金属卤化物钙钛矿在热载流子器件中的应用取决于加深对这些材料中光激发的理解。在这里，Price等人使用瞬态吸收光谱来研究CH 3 NH3 PbI 3中的热载流子分布，并量化关键的半导体参数。
Metal-halide perovskites are at the frontier of optoelectronic research due to solution processability and excellent semiconductor properties. Here we use transient absorption spectroscopy to study hot-carrier distributions in CH3NH3PbI3 and quantify key semiconductor parameters. Above bandgap, non-resonant excitation creates quasi-thermalized carrier distributions within 100 fs. During carrier cooling, a sub-bandgap transient absorption signal arises at ∼1.6 eV, which is explained by the interplay of bandgap renormalization and hot-carrier distributions. At higher excitation densities, a ‘phonon bottleneck' substantially slows carrier cooling. This effect indicates a low contribution from inelastic carrier-impurity or phonon–impurity scattering in these polycrystalline materials, which supports high charge-carrier mobilities. Photoinduced reflectivity changes distort the shape of transient absorption spectra and must be included to extract physical constants. Using a simple band-filling model that accounts for these changes, we determine a small effective mass of mr=0.14 mo, which agrees with band structure calculations and high photovoltaic performance. The use of organic–inorganic metal-halide perovskites in hot-carrier devices depends on deepening the understanding of photoexcitations in these materials. Here, Price et al. use transient absorption spectroscopy to study hot-carrier distributions in CH3NH3PbI3 and quantify key semiconductors parameters.