CH $_3$ NH $_3$ PbI $_3$晶体中电子冷却和局域化的时间分辨光电子能谱
Time resolved photoemission spectroscopy of electronic cooling and localization in CH$_3$NH$_3$PbI$_3$ crystals
摘要：
我们用双光子光电子能谱测量了CH $_3$ NH $_3$ PbI $_3$单晶的表面。我们的方法监测光激发电子的电子分布，明确区分初始热化较慢的动力学过程。报道的结果揭示了快速耗散通道的热载流子（0.25 ps），设置上限的表面诱导复合速度（$<4000$ cm/s），并揭示了显着的效果浅陷阱的电子动力学。在降解的CH $_3$ NH $_3$ PbI $_3$样品中激发电子的皮秒局域化与操作装置中光转换效率的逐渐降低一致。最小化浅陷阱密度和解决老化问题可以将太阳能电池的宏观效率提高到理论极限。
英文摘要：
We measure the surface of CH$_3$NH$_3$PbI$_3$ single crystals by making use of two photon photoemission spectroscopy. Our method monitors the electronic distribution of photoexcited electrons, explicitly discriminating the initial thermalization from slower dynamical processes. The reported results disclose the fast dissipation channels of hot carriers (0.25 ps), set a upper bound to the surface induced recombination velocity ($<4000$ cm/s) and reveal the dramatic effect of shallow traps on the electrons dynamics. The picosecond localization of excited electrons in degraded CH$_3$NH$_3$PbI$_3$ samples is consistent with the progressive reduction of photoconversion efficiency in operating devices. Minimizing the density of shallow traps and solving the aging problem may boost the macroscopic efficiency of solar cells to the theoretical limit.
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