Vapor Transport Deposition of Perovskite Photovoltaics

Hybrid halide perovskites have demonstrated remarkably high solar to electrical energy conversion efficiencies and are therefore of great interest for rapid commercialization. Popular solution-based fabrication routes based on hazardous solvents cannot be readily up-scale as required. Vapor Transport Deposition (VTD) is an alternative, low-cost manufacturing technique that has been proven before for other solar cell materials. Vapor-based processes promise to overcome many challenges imposed by solution-based techniques. Being solvent-free, they bypass solvent related challenges, namely uniform coverage of large areas, chemical compatibility, and toxicity. As a low-cost alternative to thermal evaporation, VTD has the potential to deposit organic and inorganic perovskite precursor materials either sequentially or via co-deposition. Furthermore, VTD potentially offers higher tunability of deposition parameters, to enable film growth with improved composition and microstructure control.<br/>We are currently working with a custom-made VTD system, with which we achieved champion MAPI cells of close to 12% power conversion efficiency. Now, our work is focused on optimization of deposition of lead iodide and formamidinium iodide with the aid of carrier gases. We report our progress in investigating the influence of underlaying layer, substrate and sublimation temperatures, chamber pressure and flow rate ratios on the morphology and stoichiometry of the forming perovskite film, and in turn, its photo-active and electronic properties.