Short-length and high-density TiO2 nanorod arrays for the efficient charge separation interface in perovskite solar cells

The TiO2 nanorod arrays with the length of 70 nm, the diameter of 20 nm, and the areal density of 1000 µm−2 were prepared by the hydrothermal method using the aqueous grown solution of 38 mM titanium isopropoxide and 6 M hydrochloric acid at 170 °C for 60 min. The optimal annealing temperature of TiO2 nanorod arrays was 450 °C. The perovskite solar cells based on the TiO2 nanorod array and 560 nm-thickness CH3NH3PbI3−xBrx absorber layer exhibited the best photoelectric conversion efficiency (PCE) of 15.93% and the average PCE of 13.41±2.52%, while the corresponding planar perovskite solar cells without the TiO2 nanorod array and with 530 nm-thickness CH3NH3PbI3−xBrx absorber layer gave the best PCE of 12.82% and the average PCE of 10.54±2.28% at the relative humidity of 50-54%.307