Dense Perovskite Thick Film Enabled by Saturated Solution Filling for Sensitive X-ray Detection and Imaging

Thick polycrystalline perovskite films synthesized by using solution processes show great potential in X-ray detection applications. However, due to the evaporation of the solvent, many pinholes and defects appear in the thick films, which deteriorate their optoelectronic properties and diminish their X-ray detection performance. Therefore, the preparation of large area and dense perovskite thick films is desired. Herein, we propose an effective strategy of filling the pores with a saturated precursor solution. By adding the saturated perovskite solution to the polycrystalline perovskite thick film, the original perovskite film will not be destroyed because of the solution-solute equilibrium relationship. Instead, it promotes in situ crystal growth within the thick film during the annealing process. The loosely packed grains in the original thick perovskite film are connected, and the pores and defects are partially filled and fixed. Finally, a much denser perovskite thick film with improved optoelectronic properties has been obtained. The optimized thick film exhibits an X-ray sensitivity of 1616.01 μC Gy_air^-1 cm^-2 under an electric field of 44.44 V mm^-1 and a low detection limit of 28.64 nGy_air s^-1 under an electric field of 22.22 V mm^-1. These values exceed the 323.86 μC Gy_air^-1 cm^-2 and 40.52 nGy_air s^-1 of the pristine perovskite thick film measured under the same conditions. The optimized thick film also shows promising working stability and X-ray imaging capability.