Predictions of moiré excitons in twisted 2D organic–inorganic halide perovskites
Linghai Zhang a
a Nanjing Tech University, Xin Mo Fan Ma Lu, 5, Nanjing Shi, China
Proceedings of International Online Conference on Hybrid Materials and Optoelectronic Devices (HYBRIDOE21)
Online, Spain, 2021 December 15th - 17th
Organizers: Jinwei Gao, Hua Yu, Dewei Zhao, Haizheng Zhong, Hairen Tan and Xueqing Xu
Oral, Linghai Zhang, presentation 006
Publication date: 3rd December 2021

Recent breakthrough in synthesizing arbitrary vertical heterostructures of Ruddlesden–Popper (RP) perovskites opens doors to myriad quantum optoelectronic applications. However, it is not clear whether moiré excitons and flat bands can be formed in such heterostructures. Here, we predict from first principles that twisted homobilayers of RP perovskite, MA2PbI4, can host moiré excitons and yield flat energy bands. The moiré excitons exhibit unique and hybridized characteristics with electrons confined in a single layer of a striped distribution while holes localized in both layers. Nearly flat valence bands can be formed in the bilayers with relatively large twist angles, thanks to the presence of hydrogen bonds that strengthen the interlayer coupling. External pressures can further increase the interlayer coupling, yielding more localized moiré excitons and flatter valence bands. Finally, electrostatic gating is predicted to tune the degree of hybridization, energy, position and localization of moiré excitons in twisted MA2PbI4 bilayers.

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