Highly Compact TiO2 Films by Spray Pyrolysis and Application in Perovskite Solar Cells

Abstract

Transparent and pinhole free hole‐blocking layers such as TiO2 grown at low temperatures and by scalable processes are necessary to reduce production costs and thus enabling commercialization of perovskite solar cells. Here, the authors compare the transport properties of TiO2 compact layers grown by spray pyrolysis from commonly used titanium diisopropoxide bisacetylacetonate ([Ti(OPri)2(acac)2]) precursor to films grown by spray pyrolysis of TiCl4. Spray pyrolysis provides insights into the interdependence of precursor chemistry and electron transport properties of TiO2 films and their influence on the performance of the perovskite solar cells. X‐ray diffraction and X‐ray photoelectron spectroscopy data confirm the chemical and structural composition of the obtained films. Thin film deposition at lower temperature (150 °C) are conducted using TiCl4 to evaluate the influence of crystal growth and topography by scanning electron microscopy and atomic force microscopy as well as thickness (profilometry) and transmittance (UV/Vis spectroscopy) on the power conversion efficiency of perovskite solar cells. TiO2 compact layers grown from TiCl4 enhance the power conversion efficiency by acting as superior electron transfer medium and by reducing hysteresis behavior, when compared to films grown using titanium diisopropoxide bisacetylacetonate. UV/Vis spectroscopy and external quantum efficiency studies reveal the correlation of transmittance on the power conversion efficiency.