High-Performance and Stable Semi-Transparent Perovskite Solar Cells Through Composition Engineering

Semi-transparent perovskite solar cells (ST-PeSCs) have tremendous potential as solar windows owing to their higher efficiency and visible transmittance compared to amorphous silicon analogues. However, studies towards this application are still nascent, particularly in unravelling the interplay between how the perovskite composition impacts the achievable device performance and stability. Here, we study the role of A- and X-site modification in the APbX3 hybrid organic-inorganic perovskites to understand their influence on both of these factors. Through detailed experimental and simulation work, it is found that a perovskite composition consisting of caesium (Cs) and formamidinium (FA) at the A-site delivers the best device performance over a range of band gaps, which are tuned by changes to the X-site anion. Using this optimized perovskite composition, we achieve record power conversion efficiencies for ST-PeSCs with average visible transmittance values between 20 and 50%. Furthermore, the CsFA-based ST-PeSCs show excellent long-term stability in studies under continuous illumination and device heating. The stability of the precursor solutions across each of the studied compositions has also been considered. These have exposed dramatic differences in the structural properties of the perovskites and their device performance for all mixed A-site compositions possessing the archetypal methyl ammonium species, while also confirming the superior stability of the CsFA precursor solutions.