标题： 甲基铵铅卤化物钙钛矿中的间接到直接带隙转变 显示英文标题

标题： Indirect to direct bandgap transition in methylammonium lead halide perovskite

摘要： 甲基铵铅碘钙钛矿被认为是直接带隙半导体。 在这里，我们表明实际上它们的带隙在直接带隙跃迁以下60 meV处呈现弱间接带隙。 这是由于自旋-轨道耦合导致导带出现Rashba分裂的结果。 带隙的间接性质解释了强吸收和长载流子寿命之间的明显矛盾。 在环境压力到325 MPa的静水压力下，由于晶体结构的压力诱导有序化，Rashba分裂减小。 带隙的性质变得越来越直接，导致载流子复合速度加快五倍，并使辐射效率翻倍。 在高于325 MPa的静水压力下，MAPI发生可逆相变， resulting in a purely direct bandgap semiconductor. 压力引起的改变表明了外延和合成路线以实现更高效率的光电子器件。 显示英文摘要

摘要： Methylammonium lead iodide perovskites are considered direct bandgap semiconductors. Here we show that in fact they present a weakly indirect bandgap 60 meV below the direct bandgap transition. This is a consequence of spin-orbit coupling resulting in Rashba-splitting of the conduction band. The indirect nature of the bandgap explains the apparent contradiction of strong absorption and long charge carrier lifetime. Under hydrostatic pressure from ambient to 325 MPa, Rashba splitting is reduced due to a pressure induced ordering of the crystal structure. The nature of the bandgap becomes increasingly more direct, resulting in five times faster charge carrier recombination, and a doubling of the radiative efficiency. At hydrostatic pressures above 325 MPa, MAPI undergoes a reversible phase transition resulting in a purely direct bandgap semiconductor. The pressure-induced changes suggest epitaxial and synthetic routes to higher efficiency optoelectronic devices.