This PFI: AIR Technology Translation project focuses on translating reactive ink science and technology to fill the need for low temperature, high performance and low-cost photovoltaic metallization. The development of reactive inks for solar cells is important because of the savings incurred by reducing the total amount of precious silver and also because the outstanding electrical properties these inks have shown can significantly enhance photovoltaic performance while reducing the overall cost of solar energy.

The project will result in a proof-of-concept demonstration that reactive silver inks can replace costly high temperature pastes and low-temperature nanoparticle pastes in solar cell metallization. This reactive silver ink has the following unique features: resistivity comparable to metallic silver, 3.7 micro-ohm-cm, and contact resistances of 1.8 ohm-cm2 on silicon heterojunction cells, even when printed below 90°C. These features enable solar cell field factor (FF) higher than 70% and Power conversion Efficiencies higher than 18%, with much finer control of the finger width and silver consumptions an order of magnitude lower when compared to the state-of-the-art solar cell heterojunction market space.

This project addresses the following technology gap as it translates from research discovery toward commercial application. The further reduction of the contact resistance to values below 1.2 ohm-cm² is required to propel solar cell efficiencies above 20%. The project will approach this by optimizing the ink chemistry and developing adhesion promoters. While SiO2 particles could be easily incorporated like traditional silver pastes do to enhance adhesion, these glass frits require high temperatures (>350 deg. C) to form Ohmic contact. The proposed project will look into implementing Sn- and Sn/Pd-based promoters, commonly used in electrochemical and electroless deposition of noble metals on polymers and oxide surfaces. The goal is to print the entire metallization layer, metal plus the adhesion promoter. This reduces capital equipment costs, speeds production, simplifies synthesis, and reduces metal contamination across the cell.

In addition, personnel involved in this project, two graduate students, will receive hands-on experience developing products for commercial applications while working closely with industry partners. They will also receive technology transfer experience by learning about Phase I SBIR funding opportunities and other entrepreneurial training through the Arizona Technology Transfer Office.

The project engages two important partners: Techniq Inc. (advanced metallization experts) and Simplexity Product Design (printer designers) to allow for pilot testing environment, guided commercialization and the joint development of high throughput, low cost capital equipment.