Single-crystalline hybrid halide perovskites : heterostructure growth and electroluminescence characteristics

• Main Author: Hettiarachchi, Hetti Arachchilage Chathuranga
• Other Authors: Dang Cuong H.
• Format: Thesis-Doctor of Philosophy
• Language: English
• Published: Nanyang Technological University 2020
• Subjects: Engineering::Electrical and electronic engineering::Semiconductors; Engineering::Electrical and electronic engineering::Optics, optoelectronics, photonics
• Online Access: https://hdl.handle.net/10356/136632
• Institution: Nanyang Technological University

Mobile ions play a crucial role in hybrid halide perovskites, especially as single crystals, from heterostructure growth to optoelectronic properties. Heterostructure growth in the solvothermal route was known to be severely affected by the halide ion interdiffusion process. Optimizing the solution concentration and growth temperature systematically is recognized as the key to limit ion interdiffusion. We demonstrate a controlled perovskite heterostructure for the first time, with detailed characterization. As there is widespread use of semiconductor heterostructure in modern optoelectronic devices, our new structures promise many potential applications. In addition to the diffusion process under neutral conditions, some ions also can drift within the crystal under an electric field, which is important to investigate for optoelectronic applications. However, the exact mechanism still remains elusive. Unlike electrons and holes, the ions cannot be injected or extracted from electrodes and therefore accumulate at the interface. Putting this phenomenon to use, a temporary junction can be formed. However, it is critical to isolate this effect from external factors such as grain boundary mechanisms and surface reactions with moisture and air. A fully encapsulated metal-semiconductor-metal single crystal device is introduced, which can be ‘configured’ with an electric field for electroluminescence. Our newly developed technique enables an encapsulated pristine device throughout the full process from fabrication to characterization. The device exhibits the native signatures of ionic drift within a perovskite single crystal, leading to a fascinating electroluminescence blinking behavior and a slow, quasi-periodic current oscillation, even at constant bias conditions. The thesis’ results show both drift and diffusion processes of ionic species within perovskite single crystals. Our ionic diffusion control approach enables single-crystal perovskite hetero structures, while our investigation of ionic drift provides essential insights on the physics of the material for optoelectronic applications.