The influence of surface defects in SnO2 thin films prepared from different alcohol solvents on electron transport in polymer solar cells

The study demonstrates the influence of surface defects in tin dioxide (SnO₂) thin films, formed by synthesis from different alcoholic solvents, on efficiency of a polymer solar cell. The influence of the boiling point of alcohol solvents on the surface properties and the quality of the boundary interface of SnO₂ films was established. It is shown that the optical bandgap width and Urbach energy depend on the defectiveness of the SnO₂ thin films prepared from different alcoholic solvents. According to EDX data, all prepared films exhibit better stoichiometry. It has been established that the luminescence spectra of the films are associated with the formation of three emission centers, formed by defects such as interstitial tin or oxygen vacancies. Raman spectroscopy measurements of the films indicate the presence of oxygen vacancies, with their surface concentration depending on the type of alcohol solvent used in the synthesis. It is shown that in organic solar cells, the defectiveness of the SnO₂ film structure significantly affects the density of injected electrons in SnO₂. It is demonstrated that in SnO₂ films synthesized using butanol, the lower concentration of surface defects reduces electron-hole recombination at the PTB7-TH:ITIC/SnO₂ interface, resulting in an increase in the values of the OSC current-voltage characteristics.