Low Cost Direct-Write Contacts and Interconnects for Thin Film Solar

Problem: While the photovoltaic manufacturing market is dominated by foreign-produced Si, US manufacturing has an edge in the mature cadmium telluride (CdTe) industry with rapidly-growing companies such as Toledo Solar, our development partner, and First Solar leading this market. The back contact in a CdTe device has traditionally been made using copper-doped zinc telluride (ZnTe:Cu) or high work function metals such as molybdenum and tellurium, both of which rely upon metal sputtering systems that are energy-intensive, expensive to purchase and maintain, and also require multiple laser scribing steps for interconnection of cells. Crucially, these contacts result in detrimental energetic barriers, known as Schottky barriers, lowering cell efficiency ultimately limiting the maximum efficiency of the solar cells as other aspects of CdTe improve. Solution: NanoSpray’s innovative contact ink will revolutionize how CdTe back contacts are manufactured. NanoSpray’s inks leverage next-generation nanomaterials that form ideal electrical contact to CdTe and can replace sputter deposition with inexpensive solution processing. Direct-writing of NanoSpray’s ink will allow for precise control of device contacts and interconnects and remove the need for two out of three laser scribes in the manufacturing process. We anticipate that our technology will lower the production cost and improve the efficiency of CdTe PV. Phase I Plan: In Phase I, we plan to use inkjet printing to deposit NanoSpray inks as contacts and interconnects. Inkjet printing has very precise control of linewidth and location while maintaining high throughput (Aim 1). Direct-writing will also allow us to make semi-transparent contacts to maintain high conductivity and beneficial electronic properties, while simultaneously allowing light ingress to the backside of the module, allowing for potential future bifacial and tandem configurations (Aim 2). Finally, we will scale up to develop monolithically integrated modules that do not require the P3 scribe (Aim 3). Public Benefit: The success of NanoSpray’s innovation would benefit thin-film PV manufacturers, solar developers, and residential solar consumers. As the solar economy scales to meet growing demand for renewable energy, this will enable US thin-film manufacturers to compete on the global market, and ensure greater market penetration of US-made thin-film solar. There will be an additional indirect benefit to society, as deployment of renewable energy offsets the fossil fuels responsible for localized effects such air pollution, as well as global effects such as climate change and ocean acidification.