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

We report a suitable Li-doped NiO_x 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 NiO_x used as hole-extraction layer can be prepared by facile method of just adding Li source to NiO_x precursor solution to form Li-doped NiO_x layer. The presence of Li in NiO_x layer has an influence on conductivity of the NiO_x layer which is evidenced by the conductive AFM. In addition, the NiO_x 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 NiO_x hole-extraction layer is improved with significantly enhanced fill factor leading to increase in conversion efficiency of 15.41%.