The effect of solution processed nickel oxide and nickel oxide by-products on planar MAPbI3 perovskite solar cells

This study elucidated the influence of a nickel oxide inorganic hole transporting layer and its by-products produced with and without additives on planar MAPbI3 perovskite solar cell performance. We found out that NiO films produced from additive-free solution demonstrate a higher concentration of by-products in the form of Ni(OH)2. The additives enhanced the NiO concentration in final films, reducing the Ni(OH)2 concentration and improving morphology and crystallinity of the upper perovskite layer. The possible chemical reactions for NiO formation with and without additives were proposed and proved by the results of XPS and Zeta potential studies. After adding additives, with the decrease in the Ni(OH)2 concentration, the amount of by-product NiOOH had been increased, and both Ni(OH)2 and NiOOH influence the final amount of NiO in the resulting films. The effects of the NiO concentration and additives such as ethanolamine, diethanolamine, and triethanolamine have been studied for the planar MAPbI3 perovskite solar cell performance. The best devices based on additive-free NiO films of 25 mg/ml concentration exhibited a power conversion efficiency of 11.02%, while NiO with diethanolamine additive films demonstrated a power conversion efficiency of 15.4%.