The U.S. Department of Energy, under the Photovoltaics Research and Development (PVRD) program, awarded Walajabad Sampath with the Small Innovative Project in Solar (SIPS) award, to investigate improved solar energy efficiency without substantially increasing manufacturing costs. Implementing CdTe (cadmium telluride) solar electricity as a major source of energy throughout the world would not only give third-world nations access to affordable electricity, but address climate change by reducing greenhouse gases in our atmosphere.
Since 1991, Sampath’s research group at the Center for Next Generation Photovoltaics has been at the forefront of CdTe thin-film solar cell research. In the last few years, achieving higher solar cell efficiency without increasing the cost of manufacturing has become a growing challenge in the field.
Currently, the lowest cost of electricity recorded using CdTe solar panel technology without government subsidy is ¢3.8/kWh. This is substantially lower than the average cost of electricity in U.S., which is about ¢11/kWh.
Principal investigator Sampath and co-principal investigator Amit Munshi have identified the specific challenges involved, and are optimistic about bringing their research to fruition. First, they plan to investigate the use of a lower bandgap material which would allow more light to be absorbed in the solar cell leading to higher efficiency. Some initial work has been done using this method where the CdTe layer was graded with selenium (Se). This formed a CdSeTe layer where the light first hits the solar cell, then gradually turns into CdTe. Initial results using this method have led to the demonstration of 19.1% efficient CdTe solar cell. This is the highest solar cell efficiency demonstrated using CdTe by any university or national laboratory in the world, and demonstrated even higher at 22.1% by First Solar Inc.
The second major challenge that Sampath and Munshi will focus on is the limitation in voltage of these solar cells due to the inefficient doping of CdTe. This is a fundamental challenge identified by researchers globally. In an attempt to remedy the issue, a metal organic chemical vapor deposition gas with a group V dopant will be injected during deposition of CdTe films. If successful, this will be the first-ever polycrystalline CdTe solar cell of its kind to produce 1 V with only 3-5 micrometers of material.
“We truly enjoy our work in this exciting and fast-paced field and look forward to paving the way for a new breed of highly-efficient, affordable, and sustainable solar technology to advance the industry further,” said Munshi.
The Center for Next Generation Photovoltaics is a National Science Foundation supported Industry-University Cooperative Research Center. Commercial members include leaders from the energy sector and across the solar technology chain.