Ultrafast spectroscopy of hot carrier cooling in metal halide perovskite semiconductors

金属卤化物钙钛矿正迅速成为用于光电子器件的优秀半导体，包括用于太阳能的光伏。电子-声子相互作用控制着金属卤化物钙钛矿中电荷的本征迁移率，并决定了载流子能量损失的速率。太阳能电池中的高能载体通常会以热量的形式损失掉多余的能量，而不是有效地发电。在这个项目中，我们将使用超快暂态吸收光谱和光泵浦、太赫兹探测光谱相结合的方法，直接研究不同组成的钙钛矿中的载流子迁移率和冷却动力学。将开发一个模型来提供实验载流子冷却动力学的定量描述，无论有没有大量的热声子。结合实验和理论的理解，可以建立不同金属阳离子(如铅或锡)和不同卤化物阴离子(如I或Br)的合金冷却动力学的变化。其目的是提供对改变载流子冷却的因素的基本见解，以便确定在未来的器件架构中使用热载流子的可能性。

Metal halide perovskites are rapidly emerging as outstanding semiconductors for optoelectronic devices, including as a photovoltaic for solar power. The electron-phonon interaction controls the intrinsic mobility of charges in metal halide perovskites, and determines the rate at which carriers lose energy. Energetic carriers in a solar cell typically lose their excess energy as heat, rather than usefully contributing to power generation. In this project the carrier mobility and cooling dynamics will be directly examined using a combination of ultrafast transient absorption spectroscopy and optical pump, THz probe spectroscopy, in perovskites with different compositions. A model will be developed to provide a quantitative description of the experimental carrier cooling dynamics, both with and with out a substantial population of hot phonons. The combined understanding from experiment and theory will allow changes in cooling dynamics for alloys with different metal cations (e.g. Pb or Sn) and different halide anions (e.g. I or Br) to be established. The aim is to provide fundamental insights into factors that alter carrier cooling in order to establish the potential to use hot carriers in future device architectures.