Elkins Madeline H, Pensack Ryan, Proppe Andrew H, Voznyy Oleksandr, Quan Li Na, Kelley Shana O, Sargent Edward H, Scholes Gregory D
Department of Chemistry, Princeton University , Princeton, New Jersey 08544 United States.
Department of Electrical and Computer Engineering, University of Toronto , Toronto, Ontario M5S 3G4, Canada.
J Phys Chem Lett. 2017 Aug 17;8(16):3895-3901. doi: 10.1021/acs.jpclett.7b01621. Epub 2017 Aug 7.
Quasi-two-dimensional lead halide perovskites, MAPbX, are quantum confined materials with an ever-developing range of optoelectronic device applications. Like other semiconductors, the correlated motion of electrons and holes dominates the material's response to optical excitation influencing its electrical and optical properties such as charge formation and mobility. However, the effects of many-particle correlation have been relatively unexplored in perovskite because of the difficultly of probing these states directly. Here, we use double quantum coherence spectroscopy to explore the formation and localization of multiexciton states in these materials. Between the most confined domains, we demonstrate the presence of an interwell, two-exciton excited state. This demonstrates that the four-body Coulomb interaction electronically couples neighboring wells despite weak electron/hole hybridization in these materials. Additionally, in contrast with inorganic semiconductor quantum wells, we demonstrate a rapid decrease in the dephasing time as wells become thicker, indicating that exciton delocalization is not limited by structural inhomogeneity in low-dimensional perovskite.
准二维卤化铅钙钛矿（MAPbX）是量子受限材料，在光电器件应用领域的发展范围不断扩大。与其他半导体一样，电子和空穴的相关运动主导着材料对光激发的响应，影响其电学和光学性质，如电荷形成和迁移率。然而，由于直接探测这些态存在困难，多粒子关联效应在钙钛矿中尚未得到充分研究。在这里，我们使用双量子相干光谱来探索这些材料中多激子态的形成和定位。在最受限的区域之间，我们证明了存在一个阱间双激子激发态。这表明，尽管这些材料中的电子/空穴杂化较弱，但四体库仑相互作用使相邻阱发生电子耦合。此外，与无机半导体量子阱不同，我们证明随着阱变厚，退相时间迅速缩短，这表明激子离域不受低维钙钛矿结构不均匀性的限制。
