420 Nm Thick CH3NH3PbI3−xBrx Capping Layers for Efficient TiO2 Nanorod Array Perovskite Solar Cells*

The rutile TiO2 nanorod arrays with 240 nm in length, 30 nm in diameter, and 420 μ m − 2 in areal density were prepared by the hydrothermal method to replace the typical 200–300 nm thick mesoporous TiO2 thin films in perovskite solar cells. The CH3NH3PbI3−x Br x capping layers with different thicknesses were obtained on the TiO2 nanorod arrays using different concentration PbI 2 · DMSO complex precursor solutions in DMF and the photovoltaic performances of the corresponding solar cells were compared. The perovskite solar cells based on 240 nm long TiO2 nanorod arrays and 420 nm thick CH3NH3PbI3−x Br x capping layers showed the best photoelectric conversion efficiency (PCE) of 15.56% and the average PCE of 14.93±0.63% at the relative humidity of 50%–54% under the illumination of simulated AM 1.5 sunlight ( 100 mW · cm − 2 ).