Thickness optimization of nickel oxide (NiO) hole transport layers for bifacial perovskite solar cells

Over the past few years, perovskite solar cells have received significant interest in photovoltaic research due to the rapidly increasing power conversion efficiencies. It is important to design optimized material processing methods and interface engineering solutions. Here, we report a new pathway of depositing nickel oxide (NiO) thin films which would enhance the overall efficiency of the perovskite solar cells. The deposition of NiO layers (20, 50, 80, and 100 nm) on glass substrates/FTO/TiO_x (100 nm) was carried out using e-beam evaporation method. NiO films deposition at 200 C exhibited good performance in terms of electrical conduct when compared to other conditions. Later, ITO films (80 nm) were deposited at room temperature on NiO stacked films to understand the optical properties. These optimized NiO layers were later transferred into perovskite solar cells with FTO/TiO₂/MAPbI₃/NiO/ITO structure, and the device performance was further assessed with the help of SCAPS-1D simulations. The simulation outcomes show that switching the device architecture to bifacial to monofacial can significantly influence the performance of PSC and that the efficiency of the individual layers can be significantly increased by optimal optimization of the entire device. The optimal set up gives the power conversion efficiency of 28.31% for incident light coming from TiOx side, and 20.76% for incident light coming from NiO side, with a factor of bifaciality 73.12%. The reported photovoltaic parameters are simulation-based predictions using experimentally measured NiO film properties without experimentally demonstrated device efficiencies.