Enhancement of Perovskite Solar Cells Efficiency using N-Doped TiO Nanorod Arrays as Electron Transfer Layer.

In this paper, N-doped TiO (N-TiO) nanorod arrays were synthesized with hydrothermal method, and perovskite solar cells were fabricated using them as electron transfer layer. The solar cell performance was optimized by changing the N doping contents. The power conversion efficiency of solar cells based on N-TiO with the N doping content of 1% (N/Ti, atomic ratio) has been achieved 11.1%, which was 14.7% higher than that of solar cells based on un-doped TiO. To get an insight into the improvement, some investigations were performed. The structure was examined with X-ray powder diffraction (XRD), and morphology was examined by scanning electron microscopy (SEM). Energy dispersive spectrometer (EDS) and Tauc plot spectra indicated the incorporation of N in TiO nanorods. Absorption spectra showed higher absorption of visible light for N-TiO than un-doped TiO. The N doping reduced the energy band gap from 3.03 to 2.74 eV. The photoluminescence (PL) and time-resolved photoluminescence (TRPL) spectra displayed the faster electron transfer from perovskite layer to N-TiO than to un-doped TiO. Electrochemical impedance spectroscopy (EIS) showed the smaller resistance of device based on N-TiO than that on un-doped TiO.