Researchers from China's Jilin University have developed a promising method to fabricate white perovskite LEDs using lanthanides (Ln3+) ions doped CsPbCl3 perovskite nanocrystals (PeNCs).
Lead halide perovskite nanocrystals (PeNCs) have attracted extensive attention due to their high photoluminescence quantum yield (PLQY), adjustable bandgap, low cost, and excellent photoelectric properties. In recent years, perovskite based light emitting diodes (LEDs) have developed rapidly and become candidates for low-cost, solution-processing based solid-state lighting. White light perovskite LEDs are possible to be obtained by stacking different NCs with complementary emissions together in one film. However, the halide ion segregation and exchange lead to severe color instability and complex structure in mixed halide perovskite LED devices. Therefore, new technologies are required for the development of white light devices.
The research team started by doping K+ ions into the lattice, to tune the perovskite bandgap by partially substituting Cs+ ions, which are well matched to the transition energy of some Ln3+ ions from the ground state to the excited state, thereby greatly improving the Förster energy transfer efficiency from excitons to Ln3+ ions.
Then they used creatine phosphate (CP), a phospholipid widely found in organisms, as a tightly binding surface-capping multi-functional ligand to regulate the film formation and enhance the optical and electrical properties of the PeNC film.
Consequently, the Eu3+ doped PeNCs based-white LEDs showed a peak luminance of 1678 cd m-2 and a maximum external quantum efficiency (EQE) of 5.4%, demonstrating excellent performance among existing white PeNC LEDs from a single chip.
Furthermore, the method of bandgap modulation and the defect passivation were generalized to other Ln3+ ions doped perovskite LEDs and successfully obtained improved electroluminescence (EL).
This work demonstrates universal strategies in the realization of highly efficient and stable white LEDs via single-component Ln3+ ions doped PeNCs, which provides a solution for the development of low-cost and simple white perovskite LEDs.