Dangling Octahedra Enable Edge States in 2D Lead Halide Perovskites

• Published in: Advanced materials (Weinheim) Vol. 34; no. 29; pp. e2201666 - n/a
• Main Authors: Qin, Yan, Li, Zhi‐Gang, Gao, Fei‐Fei, Chen, Haisheng, Li, Xiang, Xu, Bin, Li, Qian, Jiang, Xingxing, Li, Wei, Wu, Xiang, Quan, Zewei, Ye, Lei, Zhang, Yang, Lin, Zheshuai, Pedesseau, Laurent, Even, Jacky, Lu, Peixiang, Bu, Xian‐He
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01.07.2022; Wiley-VCH Verlag
• Subjects: 2D lead halide perovskites; Carrier lifetime; Chemical Sciences; Crystal structure; dangling octahedra; edge states; Electron states; Electrons; electron–phonon interactions; Emissions control; Lead compounds; local symmetry; Materials science; Metal halides; Optoelectronic devices; Perovskites; Physics; Radiative recombination; Semiconductors; 2D lead halide perovskite; dangling octahedra; edge state; electron-phonon interaction; local symmetry; 2D lead halide perovskites; edge states; electron-phonon interactions
• ISSN: 0935-9648; 1521-4095; 1521-4095
• DOI: 10.1002/adma.202201666

The structural reconstruction at the crystal layer edges of 2D lead halide perovskites (LHPs) leads to unique edge states (ES), which are manifested by prolonged carrier lifetime and reduced emission energy. These special ES can effectively enhance the optoelectronic performance of devices, but their intrinsic origin and working mechanism remain elusive. Here it is demonstrated that the ES of a family of 2D Ruddlesden–Popper LHPs [BA2CsPb2Br7, BA2MAPb2Br7, and BA2MA2Pb3Br10 (BA = butylammonium; MA = methylammonium)] arise from the rotational symmetry elevation of the PbBr6 octahedra dangling at the crystal layer edges. These dangling octahedra give rise to localized electronic states that enable an effective transport of electrons from the interior to layer edges, and the population of electrons in both the interior states and the ES can be manipulated via controlling the external fields. Moreover, the abundant phonons, activated by the dangling octahedra, can interact with electrons to facilitate radiative recombination, counterintuitive to the suppressive role commonly observed in conventional semiconductors. This work unveils the intrinsic atomistic and electronic origins of ES in 2D LHPs, which can stimulate the exploration of ES‐based exotic optoelectronic properties and the corresponding design of high‐performance devices for these emergent low‐dimensional semiconductors. The low‐energy and long‐lived edge states of 2D lead halide perovskites arise from the rotational symmetry elevation at the crystal layer edges, which are enabled by dangling PbBr6 octahedra at the lattice terminals. These dangling octahedra with enhanced atomic vibrations can give rise to localized electronic states that enable an effective electron transport from the interior to layer edges.