Liquid phase deposition of defect-controlled SnO2 electron transport layers with functional ions for CsPbI2Br inorganic self-powered photodetectors

The SnO2 charge transfer layer is the most widely used in inorganic perovskite photodetectors. Depending on the characteristics of the metal oxide and the fabrication method to form the thin film, non-radiative recombination can be induced between it and the light absorbing layer, which has a direct effect on the dark current density and detectivity of the photodetector device. In this study, SnO2 thin films were prepared by direct synthetic growth of SnO2 in the solution phase, physically blocking the current leakage path. The synthesized thin films were also chemically passivated by controlling the functional ions in the reaction solution to the appropriate heat treatment temperature, which further suppressed the interfacial recombination. In the liquid phase deposition (LPD) process used in photocatalytic synthesis, ions in the reaction solution are considered as residues to be removed, but here the ions are used to passivate oxygen vacancies to develop modified SnO2 thin films. Reducing the oxygen vacancies caused by the functional ion passivation and optimizing the film morphology minimized the leakage current of the CsPbI2Br photodetector device, provided a favorable energy level alignment, and reduced the interfacial charge recombination in the device. As a result, the dark current density of the photodetector device containing the SnO2 thin film deposited by the tailored LPD process was reduced to 7.82 x 10- 11 A/cm2, resulting in a 16.5-fold improvement in detectivity (2.77 x1013 Jones) compared to a device fabricated by spincoating commercial SnO2 particles (1.68 x1012 Jones).