Spectrally Stable and High-Performance Perovskite Pure Blue Light-Emitting Diodes

In this project, we aim to develop metal halide perovskites-based spectrally stable, high-performance pure blue light-emitting diodes (LEDs). This research objective is crucial for the development of perovskite-based solution-processed, cost-effective next-generation solid-state lighting and display technologies. Despite achieving perovskite green and red LEDs with EQEs > 25% and luminance (L) >100000 cd/m2, the sought-after perovskite pure blue LEDs (455 nm < peak emission < 470 nm) have been lagging far behind in their performance with max. EQEs < 8% and L < 1000 cd/m2, and typically suffer from severe spectral instability due to ion migration and phase segregation. These inefficient perovskite pure blue LEDs hold back the perovskites' integration into next-generation solid-state lighting/display technologies. Here, I will design spectrally stable and efficient mixed ‘Cl/Br’ halide quasi-2D perovskite (Q2DPe) pure blue emitters through “compositional engineering”, in particular by using chlorinated bulky organic cations (BOCs) and introducing a small fraction of large size A-site cations. The resultant Q2DPe will comprise of “Cl-rich surface with homogeneous halide distribution and localized lattice distortions within the unit cell"", and are speculated to possess elevated ion migration activation energies, which will suppress ion migration and phase segregation, thereby ensuring spectral stability. Further, I will design and fabricate LEDs with interface engineering, and study LED test device structures (HTL-only and ETL-only devices) to find out suitable pairs of HTL-ETLs to achieve efficient and balanced charge carrier injection, eventually resulting in spectrally stable high-performance pure blue LEDs. The project outcomes will be spectrally stable, efficient Q2DPe pure blue emitters and high-performance pure blue LEDs with EQE > 15%, luminance > 50000 cd/m2, and lifetime > 500 h at 500 cd/m2, which largely exceeds the current state-of-the-art.