Lead halide perovskite materials have been extensively used in lasers, photodetectors, and light-emitting diodes. They exhibit excellent properties such as high optical absorption coefficient, high carrier mobility, long charge-diffusion length and low defect state concentration.
Spin coated perovskite thin film has been widely applied in various optoelectronic devices. Yet, high-density grain boundaries in polycrystalline film result in higher trap states, which associates with nonradiative recombination and influences the charge-carrier lifetime, leading to a worse device performance.
Compared with polycrystalline film，perovskite single-crystal films (SCFs) with lower trap density and larger carrier mobility could enhance the device property. However, the growth of large-scale perovskite SCFs with high optical gain remains challenging.
Recently, a research team led by Prof. LIU Xinfeng from the National Center for Nanoscience and Technology (NCNST) and Profs. HU Xiaoyong, ZHANG Qing from Peking University fabricate large-scale thin CsPbBr3 SCFs on the c-plane sapphire substrate. The research is published on ACS Nano.
CsPbBr3 SCFs are obtained by altering the temperature and reactant concentration of vapor-phase epitaxy (VPE). Morphology and structure characterization (Figure 1) suggest high crystal quality and low defect density.
Optical gain of the SCFs are analyzed. The amplified spontaneous emission (ASE) threshold value is 8 μJ cm-2, and the measured optical gain coefficient is 1255 ± 160 cm-1which is the largest reported value for CsPbBr3 film.
CsPbBr3 SCFs are etched by focused ion beam (FIB) to prepare CsPbBr3 micro plate array. Lasing behavior was observed in the array (Figure 2) with the threshold of 1.6 μJ cm-2. These performances promise the possibility of CsPbBr3 SCFs for future integrated optical applications.
The research is supported by Strategic Priority Research Program of Chinese Academy of Sciences, the Ministry of Science and Technology, National Natural Science Foundation of China, and Open Research Fund Program of the State Key Laboratory of Low-Dimensional Quantum physics.
Figure 1. The growth schematic, morphology and structure characterization of CsPbBr3 SCEs
Figure 2. Lasing characterization of CsPbBr3 microdisk array