Highly Efficient and Uniform 1 cm2 Perovskite Solar Cells with an Electrochemically Deposited NiOx Hole-Extraction Layer

Given that the highest certified conversion efficiency of the organic–inorganic perovskite solar cell (PSC) already exceeds 22 %, which is even higher than that of the polycrystalline silicon solar cell, the significance of new scalable processes that can be utilized for preparing large-area devices and their commercialization is rapidly increasing. From this perspective, the electrodeposition method is one of the most suitable processes for preparing large-area devices because it is an already commercialized process with proven controllability and scalability. Here, a highly uniform NiO_x layer prepared by electrochemical deposition is reported as an efficient hole-extraction layer of a p–i–n-type planar PSC with a large active area of >1 cm². It is demonstrated that the increased surface roughness of the NiO_x layer, achieved by controlling the deposition current density, facilitates the hole extraction at the interface between perovskite and NiO_x, and thus increases the fill factor and the conversion efficiency. The electrochemically deposited NiO_x layer also exhibits extremely uniform thickness and morphology, leading to highly efficient and uniform large-area PSCs. As a result, the p–i–n-type planar PSC with an area of 1.084 cm² exhibits a stable conversion efficiency of 17.0 % (19.2 % for 0.1 cm²) without showing hysteresis effects.