Chen Xihan, Lu Haipeng, Wang Kang, Zhai Yaxin, Lunin Vladimir, Sercel Peter C, Beard Matthew C
National Renewable Energy Laboratory, Golden, Colorado 80401, United States.
Department of Mechanical and Energy Engineering, Southern University of Science and Technology, Shenzhen, Guangdong 518055, China.
J Am Chem Soc. 2021 Nov 24;143(46):19438-19445. doi: 10.1021/jacs.1c08514. Epub 2021 Nov 12.
Metal-halide perovskite semiconductors have attracted attention for opto-spintronic applications where the manipulation of charge and spin degrees of freedom have the potential to lower power consumption and achieve faster switching times for electronic devices. Lower-dimensional perovskites are of particular interest since the lower degree of symmetry of the metal-halide connected octahedra and the large spin-orbit coupling can potentially lift the spin degeneracy. To achieve their full application potential, long spin-polarized lifetimes and an understanding of spin-relaxation in these systems are needed. Here, we report an intriguing spin-selective excitation of excitons in a series of 2D lead iodide perovskite ( = 1) single crystals by using time- and polarization-resolved transient reflection spectroscopy. Exciton spin relaxation times as long as ∼26 ps at low excitation densities and at room temperature were achieved for a system with small binding energy, 2D EOAPbI (EOA = ethanolamine). By tuning the excitation density and the exciton binding energy, we identify the dominant mechanism as the D'yakonov-Perel (DP) mechanism at low exciton densities and the Bir-Aronov-Pikus (BAP) mechanism at high excitation densities. Together, these results provide new design principles to achieve long spin lifetimes in metal-halide perovskite semiconductors.
金属卤化物钙钛矿半导体在光自旋电子学应用中受到了关注，在这些应用中，对电荷和自旋自由度的操控有可能降低功耗，并实现电子设备更快的开关时间。低维钙钛矿尤其令人感兴趣，因为金属卤化物连接的八面体的对称性较低以及大的自旋轨道耦合有可能消除自旋简并。为了充分发挥其应用潜力，需要在这些系统中实现长的自旋极化寿命并了解自旋弛豫。在此，我们通过使用时间分辨和偏振分辨瞬态反射光谱，报道了在一系列二维碘化铅钙钛矿（n = 1）单晶中激子的一种有趣的自旋选择性激发。对于具有小结合能的二维EOAPbI（EOA = 乙醇胺）系统，在低激发密度和室温下实现了长达约26 ps的激子自旋弛豫时间。通过调节激发密度和激子结合能，我们确定在低激子密度下主导机制为D'yakonov-Perel（DP）机制，在高激发密度下为Bir-Aronov-Pikus（BAP）机制。总之，这些结果为在金属卤化物钙钛矿半导体中实现长自旋寿命提供了新的设计原则。
