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 perovskites 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 Navys needs for high-efficiency and lightweight photovoltaics.
Benefit: The advent of higher efficiency, lightweight, flexible, and lower cost solar cells would present a new paradigm for photovoltaics and energy production in general. III-V semiconductor based solar cells do possess the combination of high-efficiency, lightweight, and flexibility, but at a prohibitively high cost, typically 100 times the cost of terrestrial solar, making them only applicable for space applications. Perovskite-perovskite tandems uniquely offer these desirable features with a lower $/W cost floor than any other commercial solar technologies. Higher efficiency modules can provide more power, essential to area-constrained applications, while also lowering the total balance of systems costs by reducing costs such as land, labor, and racking. Additionally, current solar panels often weigh around 40-50 pounds and are nearly the size of a door, making them difficult to carry and install. Lightweight and flexible solar panels will not only offer significant savings on module racking and labor costs; they will be less than 5 pounds and able to roll or fold up, opening up numerous new opportunities for mobile applications such as for both on-land and airborne vehicle integration and transportable off-grid use. This is specifically important to military operations in remote locations and conflict zones, where the cost of transporting and deploying power is expensive and dangerous. In response to the need to reduce casualties during dangerous fuel-resupply missions, projects like the Marine Corps Ground Renewable Expeditionary Energy Network System (GREENS) have been developed which is a combined photovoltaic/battery system that can be more easily transported to remote locations. The GREENS system boasts an innovative packaging technology which can reduce the weight of a traditional ~50 lb silicon solar cell module by up to 75%, to about 12.5 lbs. Perovskite solar cells hold the promise of pushing this concept even further, as they can outperform crystalline silicon solar cells in terms of cost, weight, and efficiency. Our proposal outlines an effort to fabricate 23% efficient, flexible perovskite mini-modules which will weigh below 5 pounds for a 1m2 module (10.8 ft2), presenting a 2.5X further reduction in weight. Ultimately, Swift believes perovskite-perovskite tandems have the potential to be the lowest cost solar power solution on a system level and present an exciting solution for specialized military and mobile applications, as well as grid-scale consumer energy.
Keywords: Lightweight, Lightweight, High efficiency, flexible, tandems, Perovskite solar cells
