Solar Energy

Recent News:

Department of Energy grant aims for more efficient solar technology

“Developing CdTe homojunctions applying high throughput deposition” (2021-2022)

Funding:  Department of Energy – Office of Energy Efficiency & Renewable Energy – Solar Energy Technology Office – Small Innovative Projects in Solar

Partners:  National Renewable Energy Laboratory

In order to fabricate homojunctions, we will develop indium (In) and iodine (I)-doped n-type CdTe that is compatible with a GrV-doped p-type CdTe absorber. In this project, we will design, fabricate, and study CdTe homojunctions, combining modeling, bulk and thin film growth of doped CdTe, and material and device characterization. The junction will be made by depositing highly n-type epitaxial films on p-type single crystal substrates. A fast close-space sublimation epitaxy (CSSE) process, which has been shown to produce single crystal films, will be used to make n-type films by in-situ doping. As source material, pre-doped CdTe:In and CdTe:I materials, grown by the Bridgman method, will be used. Device modeling will be performed, which will guide desired optimization of material properties and device design for making efficient junctions.

“Developing a low cost, high volume and scalable manufacturing technology for undoped and heavily p-type doped CdTe feedstock materials” (2016-2021)

Funding:  Department of Energy – Office of Energy Efficiency & Renewable Energy – Solar Energy Technology Office – Photovoltaics Research & Development

Partners:  National Renewable Energy Laboratory, Nious Technologies

WSU Insider Article: Researchers Advance Solar Material Production

The goal is to establish a cost effective and scalable production approach of feedstock (CdTe and CdSeTe) for the solar industry, with the material properties necessary to improve performance and reduce costs. The primary focus is to develop a CdTe synthesis and growth process that pushes the p-type doping of CdTe to previously unattainable levels, while creating a path to scalable production. Based on previous results, we will aggressively explore how to effectively incorporate the p-type dopant during crystal growth. In our approach, the first step will be bulk CdTe growth doped with phosphorus using the Modified Vertical Bridgman (MVB) and high Pressure Bridgman (HPB) technique, and the second step will examine films deposited by Close-Spaced Sublimation (CSS) and Vapor Transport Deposition (VTD) using specialized feedstock. Systematic defect spectroscopy will be conducted to characterize the point and extended defect distribution.

“Preparation and evaluation of n-type CdSeTe as an absorber in thin film CdTe PV” (2019-2020)

Funding:  Department of Energy – Office of Energy Efficiency & Renewable Energy – Solar Energy Technology Office – Small Innovative Projects in Solar

Partners:  National Renewable Energy Laboratory

In the present effort we will investigate the doping efficiency of n-type CdTe and CdSeTe as potential absorber materials for thin film PV application. Initially melt growth of CdTe and CdSeTe bulk crystals doped with indium will be performed by vertical Bridgman method. The electrical property and activation of dopants in single crystals will be measured by Hall effect after determining the dopant concentration by ICP-MS. Post growth treatment of single crystals under overpressure conditions will be performed to better understand the activation. Thin films will be fabricated from the CdTe:In and CdSeTe:In targets by RF magnetron sputtering, on CdTe single crystals and other appropriate substrates.

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Selected Publications:

• Burst, J.M., J.N. Duenow, D.S. Albin, E. Colegrove, M.O. Reese, J.A. Aguiar, C.S. Jiang, M.K. Patel, M.M. Al-Jassim, D. Kuciauskas, S. Swain, T. Ablekim, K.G. Lynn, and W.K. Metzger, “CdTe solar cells with open-circuit voltage breaking the 1 V barrier,” Nature Energy, 1(3), 16015 (2016).
• Ablekim, T., S. Swain, W.-J. Yin, K. Zaunbrecher, J. Burst, T. Barnes, D. Kuciauskas, S.-H. Wei, and K. Lynn, “Self-compensation in arsenic doping of CdTe,” Scientific Reports, 7, 4533 (2017).
• McCoy, J.J., S.K. Swain, J.R. Sieber, D.R. Diercks, B.P. Gorman, and K.G. Lynn, “p-type doping efficiency in CdTe: Influence of second phase formation,” Journal of Applied Physics, 123(16), 161579 (2018).
• Perkins, C.L., T. Ablekim, T.M. Barnes, D. Kuciauskas, K.G. Lynn, W. Nemeth, M.O. Reese, S.K. Swain, and W.K. Metzger, “Interfaces Between CdTe and ALD Al2O3,” IEEE Journal of Photovoltaics, 8(6), 1858-1861 (2018).
• Swain, S.K., J.N. Duenow, S.W. Johnston, M. Amarasinghe, J.J. McCoy, W.K. Metzger, and K.G. Lynn, “Approach to Defect-Free Lifetime and High Electron Density in CdTe,” Journal of Electronic Materials, 48(7), 4235-4239 (2019).
• Al-Hamdi, T.K., S.W. McPherson, S.K. Swain, J. Jennings, J.N. Duenow, X. Zheng, D.S. Albin, T. Ablekim, E. Colegrove, M. Amarasinghe, A. Ferguson, W.K. Metzger, C. Szeles, and K.G. Lynn, “CdTe synthesis and crystal growth using the high-pressure Bridgman technique,” Journal of Crystal Growth, 534, 125466 (2020).