Optimizing Operational Stability of Lead Iodide Perovskite LEDs via Amino-Rich Cations Engineering

In recent years, metal halide perovskites have emerged as one of the most promising materials due to their excellent optoelectronic properties, such as direct adjustable bandgap, excellent carrier transport characteristics, ease of solution processability, and high solar cell power conversion efficiency (>30%). Perovskite based light emitting devices have advantages over high luminous color purity, color-tunablity, narrow-band emissions, low cost, and simple manufacturing processes, with external quantum efficiency exceeding >25%, which meet the market demand. However, there are two major issues of these perovskite based LEDs which hinders industrialization: (i) poor long-term device operational stability and (ii) poor performance in the blue regime. Perovskite LED device operation stability depends on the stability of perovskite under applied bias and the interaction at the interfaces with various charge transport layers. On the other hand, wide bandgap blue emitting perovskite thin film and nanocrystals exhibit poor photoluminescence quantum yield due to the presence of defect states. In view of the hot material prospects and major limitations on the perovskite LED research, my PhD program will intensively study the synthesis, characterization, spectroscopic investigation and LED device fabrications of metal halide perovskite in the form of nanocrystals and thin films. The effect of processing parameters (precursor ratio tuning, anti-solvent treatment and annealing temperature modulation) on the crystalline quality and optical properties (e.g. time- and temperature-dependent photoluminescence) of the perovskite will be investigated. Replacement of volatile organic cations with more stable inorganic one will improve device operation stability. Then the preparation and optimization of various charge transporting layer materials to improve perovskite devices performances and stability will be studied in detail. To understand the device operation mechanism and stability, spectroscopic investigations (e.g. lifetimes and blinking) of electroluminescence will also be done on the working LED device under applied electrical bias for the first time. This study will pave the path towards more stable, high-performance perovskite LEDs.