Uv photodetectors based on high quality cspbcl3 film prepared by a two-step diffusion method

Abstract

Visible-blind ultra-violet (UV) photodetectors have great application prospects in military and civilian fields. Hence, it is important to develop high-efficiency UV photodetectors. Perovskite materials have been widely applied in many fields, such as solar cells, light-emitting diodes, and photodetectors, owing to their excellent optical properties. The CsPbCl3 perovskite has a great potential in visible-blind UV photodetectors owing to its stable chemical properties and a suitable band gap. However, due to the extremely poor precursor solubility of CsPbCl3, it is difficult to find a suitable solvent to prepare CsPbCl3 films. In this study, we developed a two-step diffusion method to prepare CsPbCl3 films. PbCl2 and CsCl were dissolved in different solvents to overcome the solubility problem of CsPbCl3. First, the PbCl2 film was spin coated on a soda-lime glass. The CsCl solution was then continually dropwise spin-coated on the PbCl2 film to form the CsPbCl3 film. By controlling the morphology of PbCl2 through different annealing temperatures, the influence of different PbCl2 precursor films on microstructure of the CsPbCl3 film was investigated. The X-ray diffraction and scanning electron microscopy profiles of the PbCl2 precursor film and the CsPbCl3 film suggested that when the annealing temperature was too low, excess dimethyl sulfoxide (DMSO) remained in the PbCl2 precursor film, which hindered the transformation of CsPbCl3. However, when the annealing temperature was too high, voids appeared in the CsPbCl3 film due to excess DMSO volatilization, which caused pinholes in the CsPbCl3 film. Finally, a pinhole-free, smooth CsPbCl3 film with full grains was obtained when PbCl2 was annealed at 80 °C. To the best of our knowledge, this is the first time a high-quality CsPbCl3 film with 1 μm grains was prepared using a two-step diffusion method. Photoelectrical characterizations, such as ultraviolet-visible absorption, steady-state photoluminescence (PL), and time-resolved PL characterizations, were studied to evaluate the quality of the film. The as-prepared CsPbCl3 film had strong UV absorption and PL intensity, and its longer PL lifetime indicated that the film had fewer defect states. Furthermore, a UV photodetector with a lateral structure based on the CsPbCl3 film was fabricated. The related electrical characterizations, such as current voltage curves, showed a good responsivity of 0.75 A·W−1 and an outstanding detectivity of 7.8 × 1012 Jones, which are better than those of contemporary commercial photodetectors. The findings of this study show that a two-step diffusion method can be used to prepare CsPbCl3 films with better features and that it has a great potential in the development of UV photodetectors in the future.