Synthesis of tunable aryl alkyl ionic liquid-stabilized NiO nanoparticles supported reduced graphene oxide as highly efficient hole transport layer in perovskite solar cell

This research presents a new method for synthesizing nickel oxide (NiO) nanoparticles, which are stabilized using tunable aryl alkyl ionic liquids (TAAILs) and anchored onto reduced graphene oxide (RGO). The result is a nanocomposite hole transport layer (HTL) designed for perovskite solar cells (PSCs). A major advancement of this approach is its solution to the persistent issue of impurity ion contamination typically seen in conventional NiO synthesis. By introducing the imidazolium-based ionic liquid during the formation of the nanoparticles, the process effectively blocks the adsorption of nitrate ions. This leads to formation of highly pure and crystalline NiO NPs with consistent size and uniform dispersion. The RGO-NiO-IL nanocomposite seems to make the hole-transport layer rougher and more porous, which may help move charge faster and cut down recombination. In a perovskite cell it gave about 11.2 % efficiency, about twice what a plain RGO layer did. The open-circuit voltage was around 0.97 V (±0.02) and the short-circuit current about 16.2 mA/cm 2 (±0.18). Its fill factor sat near 0.71 (±0.59). After four months in normal air device kept 75 % of original power. The study suggests using an ionic liquid to grow nanoparticles together with RGO can fix many problems of pure NiO HTLs, pointing to a cheaper, more stable route for large-scale solar production.