The luminescence of CsPbCl3 film was enhanced: A CsPbCl3/Cs4PbCl6 mixed film was formed by adding excess CsCl

Abstract

In recent years, there have been numerous reports on the inter-transformation between non-luminous Cs4PbX6 nanocrystals (NCs) and luminous CsPbX3 nanocrystals (NCs). However, most of these reports have focused on the transformation between Cs4PbBr6 NCs and CsPbBr3 NCs, with little attention given to Cs4PbCl6 NCs. This paper aims to address this gap by investigating the formation of Cs4PbCl6 through the addition of excess CsCl during thermal evaporation. The presence of Cs4PbCl6 was found to passivate the CsPbCl3 film and improve its luminescence. The highest photoluminescence (PL) intensity of the sample was observed when the ratio of PbCl2 to CsCl was 1:1.17. This can be attributed to the enhanced crystal quality and reduced non-radiative recombination resulting from the presence of Cs4PbCl6. Furthermore, rapid annealing led to a two-fold increase in the PL intensity of the film. Notably, the film containing Cs4PbCl6 exhibited excellent thermal stability, maintaining a constant PL intensity within the annealing temperature range of 200°C–300 °C. This can be attributed to the prevention of grain size growth in the film due to the presence of Cs4PbCl6. Finally, the electroluminescent device test results showed that the electroluminescence intensity reached the highest at 6 V driving voltage, which was caused by the effective carrier recombination, while the ratio of PbCl2 to CsCl was 1:1.17 and the annealing temperature was 180 °C. This study provided a novel approach to enhancing the photoelectric performance of CsPbCl3.