Park Ji-Sang, Choi Sukgeun, Yan Yong, Yang Ye, Luther Joseph M, Wei Su-Huai, Parilla Philip, Zhu Kai
National Renewable Energy Laboratory , Golden, Colorado 80401, United States.
J Phys Chem Lett. 2015 Nov 5;6(21):4304-8. doi: 10.1021/acs.jpclett.5b01699. Epub 2015 Oct 15.
The electronic structure and related optical properties of an emerging thin-film photovoltaic material CH3NH3PbBr3 are studied. A block-shaped α-phase CH3NH3PbBr3 single crystal with the natural ⟨100⟩ surface is synthesized solvothermally. The room-temperature dielectric function ε = ε1 + iε2 spectrum of CH3NH3PbBr3 is determined by spectroscopic ellipsometry from 0.73 to 6.45 eV. Data are modeled with a series of Tauc-Lorentz oscillators, which show the absorption edge with a strong excitonic transition at ∼2.3 eV and several above-bandgap optical structures associated with the electronic interband transitions. The energy band structure and ε data of CH3NH3PbBr3 for the CH3NH3(+) molecules oriented in the ⟨111⟩ and ⟨100⟩ directions are obtained from first-principles calculations. The overall shape of ε data shows a qualitatively good agreement with experimental results. Electronic origins of major optical structures are discussed.
研究了一种新兴的薄膜光伏材料CH3NH3PbBr3的电子结构和相关光学性质。通过溶剂热法合成了具有天然⟨100⟩表面的块状α相CH3NH3PbBr3单晶。利用光谱椭偏仪在0.73至6.45 eV范围内测定了CH3NH3PbBr3在室温下的介电函数ε = ε1 + iε2光谱。数据用一系列Tauc-Lorentz振子进行建模，结果表明在约2.3 eV处存在具有强激子跃迁的吸收边以及与电子带间跃迁相关的几个带隙以上的光学结构。通过第一性原理计算得到了CH3NH3(+)分子沿⟨111⟩和⟨100⟩方向取向的CH3NH3PbBr3的能带结构和ε数据。ε数据的整体形状与实验结果在定性上吻合良好。讨论了主要光学结构的电子起源。
