Cu-doped nickel oxide hole transporting layer via efficient low-temperature spraying combustion method for perovskite solar cells

Nickel oxide, a potential inorganic hole transport material, has become a research hot spot in perovskite solar cells. In this work, we propose a low temperature spray combustion method to fabricate NiOx thin film which has better performance compared with the spin-coating method. The SEM images of NiOx thin films by spraying exhibit denser morphology than films by spin-coating, demonstrating the feasibility of the spray combustion method. Based on this spray combustion method, Cu is doped into the NiOx precursor solution to further overcome the low conductivity of NiOx. When the doping concentration reaches to 7%, the efficiency of the solar cell is improved from 9.08 to 11.45%. The charge transfer process at NiOx/perovskite interface is investigated by PL and TRPL measurements, the results demonstrate the fast hole extraction using Cu:NiOx thin films. In summary, the spray combustion method can efficiently prepare high-quality Cu:NiOx thin films, reduce the annealing temperature and improve the conductivity of the thin film.