The effects of interfacial dipole caused by annealing-free Al-doped NiOx in efficient perovskite solar cells

•Annealing-free, Al-doped NiOx nano-particles were synthesized and proposed.•The NiOx was employed as the hole transport layer in Perovskite photovoltaics.•An interfacial dipole of 0.3 eV was found between ITO electrode and the NiOx layer.•Hole extraction efficiency and overall device performances were greatly improved.•No Dimethyl sulfoxide additive was used in devices.