Optimization of CsPbCl3 violet/blue all-inorganic light-emitting diodes devices

Abstract

Large grain films can effectively reduce the density of defect states; however, the performance of electroluminescent (EL) devices prepared by directly annealing the light-emitting layer remains unsatisfactory. In this paper, we propose a novel preparation method aimed at solving the problem of low carrier recombination probability in films with large grains. In this experiment, an unannealed CsPbCl₃ film was grown based on an annealed CsPbCl₃ film. The experimental results indicate that, compared with the devices of single light-emitting film, the devices of double-layer film significantly improve the intensity and stability of EL. For the lower layer of CsPbCl₃, it is essential to balance the thickness and annealing parameters. The findings reveal that device performance is optimal when the annealing temperature is set at 180 °C for a thickness of 150 nm, while the upper layer thickness is maintained at 120 nm. Additionally, stability is significantly enhanced, with the device lasting for 9 min before decaying to 48 % of its initial brightness. At the same time, the full width at half maximum is only 9.7 nm, showing high color purity. This improvement can be attributed to several factors: the epitaxial growth of the annealed layer enhances grain size and minimizes the number of grain boundaries, thereby suppressing ion migration. Additionally, films with larger grains demonstrate a lower density of defect states, which can mitigate non-radiative recombination processes. Finally, a higher valence band facilitates hole injection and aids in balancing carrier transport.