Nickel oxide nanoparticles for efficient hole transport in p-i-n and n-i-p perovskite solar cells

Here, a low-temperature solution-processed nickel oxide (NiO_x) thin film was first employed as a hole transport layer in both inverted (p-i-n) planar and regular (n-i-p) mesoscopic organic–inorganic hybrid perovskite solar cells (PVSCs).