Project Name: Exploiting Fixed Charge at Selective Contacts for Silicon Photovoltaics
Funding Opportunity: Solar Energy Technologies Office Fiscal Year 2018 Funding Program (SETO FY2018)
SETO Research Area: Photovoltaics
Location: Bethlehem, PA
SETO Award Amount: $200,000
Awardee Cost Share: $50,000
Principal Investigator: Nicholas Strandwitz

-- Award and cost share amounts are subject to change pending negotiations --

This project seeks to increase the efficiency of silicon solar cells by depositing a very thin layer of metal oxide between the silicon and the metal electrical contacts. Conductive metal contacts enable electricity to flow out from the cell. Over time, an energy barrier builds up between the silicon and the metal contacts, preventing low-energy electrons from reaching the metal. This barrier reduces the electrical flow and thus the cell’s efficiency. A thin metal oxide layer between the silicon and the electrical contacts will allow the electrons to more easily pass through, leading to increased efficiency.

APPROACH

This team will use a technique called atomic layer deposition (ALD) to precisely deposit layers of aluminum oxide as thin as one-billionth of a meter onto the silicon. Depending on the details of the deposited layer, the layer will hold a specific fixed charge and reduce the energy barrier so that electrons can more easily pass from the absorbing silicon layer to the electrical contacts. The team will determine the best conditions for processing and depositing the aluminum oxide layer, such as the ideal thickness of the layer, to minimize the energy barrier and maximize the electrical flow and cell efficiency.

INNOVATION

While thin metal layers are already used in solar cells, this project is novel in that it uses the technique of ALD, rather than other more common solar cell fabrication techniques, to deposit those layers in solar cells. Using ALD, these layers can be made extremely thin, as thin as one nanometer (one-billionth of a meter). The layer will lower the energy barrier and allow more electrons to pass through as a result; but also, because the layer is so thin, it will allow additional electrons that would otherwise be unable to penetrate the remaining energy barrier to cross the barrier anyway, through a quantum-mechanical phenomenon called “tunneling.” The ALD technique is precise, controllable, and can be scaled up, meaning that it can eventually lead to commercialization of more efficient as well as less expensive solar cells.