Enhanced electrical properties of Li–doped NiOx hole extraction layer in p–i–n type perovskite solar cells

We report a suitable Li-doped NiOx hole-extraction layer of p–i–n type planar perovskite solar cell as an alternative to organic material such as PEDOT:PSS. The Li-doped NiOx used as hole-extraction layer can be prepared by facile method of just adding Li source to NiOx precursor solution to form Li-doped NiOx layer. The presence of Li in NiOx layer has an influence on conductivity of the NiOx layer which is evidenced by the conductive AFM. In addition, the NiOx layer with 50 nm thickness prevents a lot of pinholes inside the film and relatively low processing temperature of 200 °C has the advantage of wide choice of transparent conduction oxide substrate. As a result, p–i–n type planar perovskite solar cell incorporating the Li-doped NiOx hole-extraction layer is improved with significantly enhanced fill factor leading to increase in conversion efficiency of 15.41%.