SBIR-STTR Award

Solar power is one of the fastest-growing renewable energy markets. Over the last twenty years, solar photovoltaics has gone from being a field of scientific study to one of commercial interest. Driving this change and solar adoption worldwide has been the decreasing cost per watt of solar power. While the drop in cost per watt has been largely driven by increasing panel efficiency, decreasing materials costs has also been of interest. The low-iron, TCO-coated float glass used for thin-film solar cells has long been a target for cost reduction. CIGS solar cells have tried to get around this by switching away from glass to thin metal foil or polymer substrates, but for CdTe, the leading thin-film solar technology, this has not been an option. Thin-film CdTe manufacturers are locked into deposition on glass due to the high temperature steps required by the manufacturing process. CdTe manufacturers are consequently beholden to solar glass providers, who provide the coated glass needed for thin-film CdTe manufacturing. This glass, which is coated with an alkali-diffusion barrier and TCO, is expensive and difficult to source. We have developed solution-based precursors that give highly dense and smooth optically transparent films that are of use as alkali-diffusion barriers. In this Phase I project, we will extend this invention via rapid laser annealing, allowing us to deposit on soda-lime glass at low temperatures. The work will establish baseline performance by comparing FTO conductivity on coated versus uncoated alkali-containing glass. Identification of the critical factors among precursor composition, film density, alkali diffusion, optical transparency and laser annealing parameters will allow us to rapidly iterate and meet thin-film performance targets. Outcomes from Phase I will enable capabilities in Phase II to scale methods for deposition on large-area substrates via Gravure roll coating. Integration of optimized solutions, roll coating, and laser annealing represents a breakthrough manufacturing platform to reduce the costs of thin-film solar by allowing CdTe manufacturers to coat glass in their own factories, on their own product lines, without the need to invest in vapor deposition systems, reducing the costs associated with bill of materials in thin-film solar, decreasing cost-per-watt and furthering solar market growth.

Solar power is one of the fastestgrowing renewable energy markets. Over the last twenty years solar photovoltaics has gone from being a field of scientific study to one of commercial interest. Decreasing cost per watt of solar power has been a key market driver. Materials and production costs have slowed USbased growth. nexTC Corporation addresses these issues by creating lowcost materials and processes required for solar module operation. Current TCO glass products do not meet device manufacturer needs and require costly work arounds to meet performance specifications. Glass companies manufacture FTOcoated glass via chemical vapor deposition CVD. CVD produces conductive films with high surface roughness and high optical haze, both of which are incompatible with production of thin film solar modules, especially CdTebased devices. Highsurface roughness leads to propagation of defects throughout the solar stack, while high optical haze limits transparency. nexTC provides to manufacturers a TCObilayer stack that improves performance and lowers costs. Our materials are easy to deposit and process, providing solar module manufacturers the opportunity to eliminate dependence on any specific glass provider, and enables glass companies to offer a more competitive product for the broader TCO coated glass market. In the Phase 1 SBIR we demonstrated that our materials and methods to produce ultrasmooth, uniform diffusion barrier films modulate alkali metal diffusion and increase optical transmission by 5%. When combined with our proprietary solution processed TCO films, we observe optical and electrical properties that meet industry standards. nexTC’s integration of optimized chemical solutions, slotdie coating, and rapid annealing represents a breakthrough manufacturing platform to improve the efficiency of solar modules and lower manufacturing costs. The focus of this SBIR Phase II is to scale precursor synthesis, deposition area, and create second generation products based on abundant materials. nexTC will engage customers to build prototype solar modules to demonstrate efficacy on large area substrates. The platform technology developed herein has commercial applications outside of the identified beachhead market of thin film solar, including smartwindows, passivation coatings, and large area electronics.