Novel double layer atmospheric pressure chemical vapor deposition method for all inorganic perovskite synthesis: Development of PV technology stable against harsh weather conditions

Silicon based solar cells are dominating the commercial PV market. These cells have very costly fabrication process and at the same time considerable carbon footprint. So researchers around the world busy with different solar cell technologies to come up with a suitable alternative. Among the various technologies, perovskite (PVT) based solar cells (both single junction and tandem structure) showed promising results. These materials have high absorption and weak exciton recombination, which result in excellent efficiencies. Reported power conversion efficiency (PCE) of single junction PSC has improved intensely from the initial 3.9% in 2009 to 23% in a short span of time. However, commonly used organic lead halide PVT has low energy of formation, which also makes it susceptible to degradation in moisture and air. Moreover, when thermal stability is considered, organic-inorganic PVT devices found to be disreputable due the presence of the organic cation. Therefore, inorganic caesium (Cs) was used to replace the organic cation. Later several other inorganic cations have also been used. In all cases, defect free high quality PVT deposition layer is important for a better performing perovskite solar cell (PSC). Because, presence of pinhole is the main reason of shunting, which eventually reduces the open circuit voltage. Most common PVT layer deposition techniques are co-evaporation and solution process. However, these processes have failed to deliver pinhole and defect free PVT layer, especially when large area or industrial scale are considered. Atmospheric pressure chemical vapour deposition (APCVD) method is an effective process for a good quality uniform large area thin film deposition. This process can provide uniform better quality PVT layer with controlled thickness at a large scale. Moreover, in an all-inorganic PVT based PSCs, the double layered APCVD technique has hardly been reported/used. Thus, APCVD technology based PVT deposition is proposed in this project to deposit all inorganic, PVT layer with reduced defects different composition, which can open a way to get cost-effective, stable and environmental friendly PVT for future PV industries.