Vapor-Deposited, High Efficiency, and Low Weight Perovskite Tandem Solar Cells

Perovskite solar cells have gained significant attention for their rapid rise in lab-scale solar power conversion efficiency and ability to outperform crystalline silicon solar cells in terms of cost, weight, flexibility. This combination of low-cost, low-weight, flexibility, and high efficiency are enabled by the perovskite’s high optical absorption, superior defect-tolerance, and low formation energy. This means that very thin and flexible films can absorb all of the above-bandgap sunlight and they can be quickly deposited on plastic substrates at low temperatures. This is in contrast to silicon solar cells, which require thick, non-flexible wafers to absorb light and energy intensive and slow wafer growth processes. Critically, low-weight and high-efficiency are key characteristics for renewable energy deployment in conflict zones, where easy transportation of fuel and power can save lives. A 2009 study released by Deloitte found that the deployment of alternative energy could directly reduce wartime casualties with fuel resupply convoys being the most vulnerable to attack. They calculated an average of 1 casualty for every 24 fuel resupply convoys in Afghanistan, during over 900 resupply convoys a year at the time of the study. Renewable sources of energy can help mitigate the need for fuel resupply and allow for more reliable energy access in remote locations. Swift Solar is a leader in the development of lightweight, flexible, and high-efficiency perovskite-perovskite multi-junction solar cells. While perovskites can be processed via solution coating methods, non-uniformity inherent to solution methods could hinder yield and solvent compatibility and toxicity could make the manufacturing of high-efficiency tandems difficult. Vapor deposition methods are ubiquitous in the thin-film manufacturing industry for optical coatings on windows to electrical layers in computer hard drives due to their high-quality, uniformity, and yield. The goal of this SBIR is to demonstrate an all-vapor deposition methodology for high uniformity and yield to enable scale-up of manufacturing. This vapor deposition methodology is also critical to achieving high stability, which has been problematic in the past for perovskites. Swift will perform stability testing on flexible packaged perovskites to validate potential for commercial use and aim to meet the Navy’s needs for high-efficiency and lightweight photovoltaics.