SBIR Phase I: Low Damage Sputter Magnetron for Silicon Heterojunction PV Production

The broader impact/commercial potential of this Small Business Innovation Research (SBIR) Phase I project will be seen in the adoption of solar energy as a cost-competitive alternative to non-renewable energy sources. While solar energy costs have been dramatically reduced, the use of the most efficient cells is limited by manufacturing costs. The need for efficient cells - solar cells that deliver more watts per area - can be seen when considering system costs. Higher efficiency reduces all costs related to area: module components, support structures, labor, land, etc. Silicon Heterojunctions (SHJ) cells deliver leading conversion efficiencies but are manufactured with processes that require multiple passes through very expensive machines to deposit required semiconductor layers. The manufacturing cost issue has hindered adoption of the high efficiency SHJ cell technology. The project's innovation dramatically reduces the cost of the most expensive steps in SHJ cell manufacture while maintaining or improving cell performance. Potentially, the innovation could find application in other markets such as organic light emitting diodes (LEDs). The cost reduction of the SHJ cell will significantly shift the photovoltaic industry's energy conversion efficiency upward and the cost per watt downward. The proposed project addresses two shortcomings of the established manufacturing methods for SHJ solar cells. The first challenge is the deposition of the cell's transparent conductive layer, typically an alloy called indium tin oxide (ITO). Standard sputter processes used for this deposition cause damage to the underlying layers of the cell. The damage can reduce the cell performance or require additional process steps. Also, next generation concepts for SHJ cell design are even more sensitive to damage and less able to tolerate "repair" steps. The project will develop a novel low damage sputter source for the ITO deposition. The second challenge is that the semiconductor layers of the SHJ cell use costly plasma-enhanced chemical vapor deposition (PECVD) systems developed for the high value display industry. The project will direct use of the novel sputter source for deposition of the semiconductor layers as well as the ITO. Sputter is lower cost than PECVD and easily allows sequential layers of different materials to be deposited in a single, continuous flow, in-line machine. The project will demonstrate the sputter source for each of the layers as separate materials and for an SHJ cell with a fully sputtered stack of the three critical layers.