Dr. Chunyun WangTsinghua-Berkley Shenzhen Institute at Tsinghua University, China
Speech Title: Efficient lead-free warm-white emitting double perovskite quantum dots for white LEDs
Abstract: Artificial light sources play an indispensable role in daily life. Around 1/6 to 1/5 of the worldwide electricity is consumed by lighting.  These lighting sources do not only need to be efficient and reliable, but high light quality is also demanded. Quantum-dot based light emitting diodes (QLED) have higher efficiency, stability, longer lifetime and wider color gamut, compared to organic light emitting diodes. Metal halide perovskite quantum dots have gained great attention for LED research, due to their high photoluminescence quantum yield, low-cost solution processability and high tunability of emission across the entire visible spectrum. [2-3] However, the toxicity and instability of lead-containing halide perovskites against moisture and air prevent further practical applications. Highly efficient lead-free halide perovskite quantum dots are still very limited, especially for single white-emitting perovskites. The efficiency and color stability of LED devices can be improved by using a single-phase white-light emitter, as it can avoid the self-absorption and color instability problems in mixed and multiple emitters.
Here we report a highly efficient lead-free warm-white emitting quantum dot Cs2Ag0.4Na0.6InCl6, crystallizing in a lead-free double perovskite Cs2AgInCl6 structure, doped with rare earth and transition metal ions. We will talk about the synthesis and luminescence properties of the perovskite quantum dots. The influence of quantum dot structure on the luminescence properties will be discussed, and the emission mechanism will be clarified by DFT calculations. Finally, the application of the white light quantum dots in QLED devices is evaluated.