Nanostructured bilayer CuSCN@CuI thin films as efficient inorganic hole transport material for inverted perovskite solar cells

In this work, the development of bilayer CuSCN@CuI inorganic hole transport material by a simple electrochemical approach is demonstrated. The thickness and the morphology of the bilayer thin films are controlled by electrochemical potential and deposition time. Uniformly distributed triangle-shaped CuI nanosheets formation is observed at 2 min deposition time. Inverted perovskite solar cells are fabricated using electrochemically grown CuSCN@CuI bilayer and tested its photovoltaic performance. The maximum short circuit current density of 18.24 mA/cm² and open-circuit voltage of 1080 mV is achieved for uniformly distributed triangle-shaped CuI nanosheets grown at 2 min deposition time. The power conversion efficiency (PCE) of 15.58% is achieved with 1400 h of stability. The moderate thickness (~180–230 nm) of bilayer CuSCN@CuI nanostructures showed better charge transport and photovoltaic performance. The favourable band alignment of the designed CuSCN@CuI/perovskite/PC₆₁BM/Carbon delivers stable open-circuit voltage than the earlier reports. The optimized bilayer CuSCN@CuI nanostructure with carbon back contact showed improved device stability.