Extrinsic Green Photoluminescence from the Edges of 2D Cesium Lead Halides
Abstract
Since the first report of the green emission of 2D all‐inorganic CsPb2Br5, its bandgap and photoluminescence (PL) origin have generated intense debate and remained controversial. After the discovery that PL centers occupy only specific morphological structures in CsPb2Br5, a two‐step highly sensitive and noninvasive optical technique is employed to resolve the controversy. Same‐spot Raman‐PL as a static property–structure probe reveals that CsPbBr3 nanocrystals are contributing to the green emission of CsPb2Br5; pressure‐dependent Raman‐PL with a diamond anvil cell as a dynamic probe further rules out point defects such as Br vacancies as an alternative mechanism. Optical absorption under hydrostatic pressure shows that the bandgap of CsPb2Br5 is 0.3–0.4 eV higher than previously reported values and remains nearly constant with pressure up to 2 GPa in good agreement with full‐fledged density functional theory (DFT) calculations. Using ion exchange of Br with Cl and I, it is further proved that CsPbBr3−x Xx (X = Cl or I) is responsible for the strong visible PL in CsPb2Br5−x Xx . This experimental approach is applicable to all PL‐active materials to distinguish intrinsic defects from extrinsic nanocrystals, and the findings pave the way for new design and development of highly efficient optoelectronic devices based on all‐inorganic lead halides.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Jun 24, 2019
- Source ID
- 10.1002/adma.201902492
Entities
People
- Chong Wang
- Francisco C. Robles Hernández
- Guoying Feng
- Haiyan Wang
- Hector A. Calderon Benavides
- Jie Jian
- Jiming Bao
- Md. Kamrul Alam
- Qiang Li
- Qingkai Yu
- Shenyu Dai
- Shuo Chen
- Viktor Hadjiev
- Xinghua Su
- Yan Yao
- Yanan Wang
- Yizhou Ni
- Zhaojun Qin
- Zhiming Wang
Organizations
- Chang'an University
- National Natural Science Foundation of China
- National Polytechnic Institute
- Office of Naval Research
- Purdue University
- Robert A. Welch Foundation
- Sichuan University
- Texas State University
- United States Department of Energy
- University of Houston
- Yunnan University