PROJECT PROFILE: Colorado State University (PVRD)

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Project Name: Device Architecture for Next-Generation CdTe PV
Funding Opportunity: PVRD
SunShot Subprogram: Photovoltaics
Location: Fort Collins, CO
SunShot Award Amount: $899,922
Awardee Cost Share: $100,000
Project Investigator: James Sites

This project is developing a novel solar cell architecture that will increase the voltage and energy output of thin-film polycrystalline cadmium telluride (CdTe) solar cells and address the short lifetimes of photo-excited electrons in the cells. This new architecture should give the CdTe manufacturing community a novel, but highly realistic, approach for solving the voltage limitations of the CdTe technology. The resulting product will be compatible with solar-panel manufacturing at or below current cost structures.

Approach

The research team will develop a cell architecture with a thinner CdTe absorber that will remain fully depleted under operating conditions. The new device structure addresses the short lifetimes of photo-excited electrons in polycrystralline CdTe by using an internal electric field to rapidly move them to the cell’s external contact. Additional device features that will enable the thin CdTe absorber device architecture are a highly-transparent MgZnO (MZO) buffer layer tuned to an optimal conduction-band offset, an expansion of the CdTe band gap at the back of the cell with a CdMgTe-alloy layer to reflect electrons, and compositional grading of the absorber/electron-reflection interface.

Innovation

This project aims to overcome a long-standing challenge of achieving higher voltages in CdTe devices by developing a new device architecture. This new architecture will rely on the electric field assisting the collection of carriers at the contacts. The new technology could potentially lead to a 2% increase in module efficiency with a structure that costs less per unit area than the standard CdTe architecture. By further improving device performance and reducing the cost structure, this project will help reach a levelized cost of energy of $0.06 per kilowatt hour by 2020.