The effect of nitrogen doping of TiO2 compact blocking layers on perovskite solar cell performance

Abstract

In this paper, nitrogen-doped titanium oxide (N-TiO2) with different dopant concentrations (0, 0.25, 0.5, and 1 at.%) were grown on FTO substrates by spray pyrolysis and applied in perovskite solar cells (PVSC) as a compact blocking layer. Morphology, chemical and physical properties of the samples were investigated by SEM, XRD, XPS, UV–Visible, and PL characterization techniques. Measurements indicate that the device based on N-TiO2 with a nitrogen content of 0.25% exhibits higher PCE (17.83%) than the device based on un-doped TiO2 (17.04%). Results show that the lowest series resistance is obtained in the device based on 0.25% N-TiO2, leading to an increase in the fill factor (FF) parameter. Also, higher VOC of this device results from lower e-h recombination due to longer electron lifetime than the un-doped sample. In addition, a slight increase in JSC is related to the small decrease in the band gap of TiO2 with nitrogen doping. Enhanced FF, VOC, and JSC are the main reasons for the improved performance of the PVSC devices by using the optimal level of nitrogen in TiO2.