Vapor Transport Deposition for Perovskite Solar Cells

Abstract

As perovskite solar cells move closer to commercialization, vapor transport deposition (VTD) has emerged as one of the potential routes for large-scale film growth of photoactive and charge transport layers for these solar cells. 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. Co-deposition can benefit film formation by increasing the deposition speed and improving film conversion. However, current co-deposition techniques can struggle to produce high quality perovskite films, impacted by challenges associated with the thermal stability of organic precursors and by effectively using the broad deposition parameter space for controlling perovskite film growth.

Here, we use methylammonium lead iodide (MAPbI3) as an archetype perovskite to identify degradation patterns and determine conditions for high-quality film growth. We show that material degradation during sublimation affects methylammonium iodide precursor powders and their contribution to the formation of MAPbI3 films differently than is observed for degradation that is solely due to material transport through a high-temperature zone. By identifying degradation products and film formation, we identify the degradation components that most affect MAPbI3 film performance. With these considerations, we design and construct a custom VTD system for co-deposition of perovskites with a wide range of deposition parameters available for studying film growth and optimizing performance. Additional investigation systematically builds from deposition on glass to an initial demonstration of solar cells. With these results we give recommendations for improved VTD reactor design and a systematic description of conditions that aid in optimization of high-performing VTD perovskite solar cells.