Methylammonium Lead Tri-Iodide Perovskite Solar Cells with Varying Equimolar Concentrations of Perovskite Precursors

During recent years, power conversion efficiencies (PCEs) of organic-inorganic halide perovskite solar cells (PSCs) have shown remarkable progress. The emergence of various thin film deposition processes to produce perovskite films, notably using solution processing techniques, can be credited in part for this achievement. The engineering of chemical precursors using solution processing routes is a powerful approach for enabling low-cost and scalable solar fabrication processes. In the present study, we have conducted a systematic study to tune the equimolar precursor ratio of the organic halide (methylammonium iodide; MAI) and metal halide (lead iodide; PbI2) in a fixed solvent mixture of N,N-dimethylformamide (DMF):dimethylsulfoxide (DMSO). The surface morphology, optical characteristics, and crystallinity of the films produced with these four distinct solutions were investigated, and our analysis shows that the MAI:PbI2 (1.5:1.5) film is optimal under the current conditions. The PSCs fabricated from the (1.5:1.5) formulation were then integrated into the n-i-p solar cell architecture on fluorine-doped tin oxide (FTO) substrates, which exhibited a PCE of ~14.56%. Stability testing on this PSC device without encapsulation at 29 °C (ambient temperature) and 60% relative humidity (RH) under one-sun illumination while keeping the device at its maximum power point showed the device retained ~60% of initial PCE value after 10 h of continuous operation. Moreover, the recombination analysis between all four formulations showed that the bimolecular recombination and trap-assisted recombination appeared to be suppressed in the more optimal (1.5:1.5) PSC device when compared to the other formulations used in the n-i-p PSC architecture.