The National Renewable Energy Laboratory awarded funding to six projects to support its Cadmium Telluride Accelerator Consortium.
The Cadmium Telluride Accelerator Consortium （CATC）， announced last August, is a three-year program intended to accelerate the development of cadmium telluride （CdTe） technologies. The goal of the initiative is to make thin-film solar cells （made with CdTe） less expensive, more efficient and to develop new markets for thin-film products.
CdTe solar cells were first developed in the United States and make up about 20% of U.S. the market for solar modules. The Consortium intends to spur technological advancements in CdTe manufacturing that will help increase America’s competitiveness, bolster domestic innovation, and support clean electricity deployment supporting President Biden’s goal of achieving a net-zero economy by 2050.
NREL released the request for proposal notice for small projects in September 2022, and the following six projects were selected:
University of Utah
University of Utah researchers will develop bilayer stacks for back contacts to state-of-the-art CdSeTe/CdTe absorbers. The researchers will focus on p-type materials that have energy level alignment predicting hole selectivity, are amenable to passivation and have a wide gap to provide transparency for enhanced bifaciality or back mirror cell optics.
The team plans to obtain state-of-the-art absorber stacks from CTAC partners and fabricate sputtered back contacts, and will continue to develop our surface photovoltage and SPV spectroscopy techniques to characterize back contact band structure, traps, and recombination activity.
University of Delaware
Researchers at the University of Delaware intend to develop new approaches for processing Cd1-xZnxTe solar cells that overcome previously reported difficulties, such as ineffective chloride activation and passivation, which prevented the realization of high performance with increased open-circuit voltage （VOC） relative to CdTe.
The approach will be based on two hypotheses: Modification of film growth, including in situ antimony incorporation, can form more equilibrated films with reduced defects and enhanced grain sizes, reducing the need for high-temperature activation; and alternative halide activation chemistries during post-deposition treatments can minimize the deleterious effects of cadmium chloride （CdCl2） activation. A final goal of the project is to confirm the viability of Cd1-xZnxTe by demonstration of a thin-film solar cell with VOC ≥ 1.0 V.
University of South Florida
University of South Florida researchers will develop alternative device architectures based on n-type CdTe/CdSeXTe1-X（CST） thin-film absorbers to create opportunities to overcome the efficiency limitations associated with the current state-of-the-art p-type CdTe/CST solar cells.
The project aims to build upon advances in n-CdTe/CST films that demonstrated group III and VII n-type doping for CdTe films. The team will focus on the development of p-type heterojunction partners for n-CdTe/CST absorbers.
Missouri University of Science and Technology
Missouri University of Science and Technology researchers plan to enhance telerium （Te） recovery from copper processing （CP） by optimizing the current operations to capture the Te, gold （Au）， and silver （Ag） that are presently lost to tails.
The scope of work involves: advanced mineralogical analysis of different processing streams of the flotation circuit of CP ores to identify Te carriers and modes of occurrence （i.e., Te in the crystal lattice vs. Te-rich inclusions in larger minerals）； evaluation of different approaches and flow sheet options for enhanced separation of Te, Ag, and Au minerals from processing streams of CP ores; and techno-economic assessment to estimate the capital and operating costs of the developed flow sheets for successful implementation, which could increase the domestic production of Te from CP ores by at least 50%.
Arizona State University
Arizona State University researchers will combine the power of hard X-ray microscopy （XRM） and soft X-ray and electron spectroscopies to probe arsenic （As）-doped CdSeTe absorbers and devices. XRM will probe the chemical distribution, atomic environment, and current collection at the nanoscale for the As and selenium （Se） absorption edges. Electron and soft X-ray spectroscopies will enable an area-integrating determination of the electronic structure at surfaces （band edges, surface bandgap） and interfaces （band alignment）， in addition to the chemical bonding environment of the sulfur （S）， chlorine （Cl）， and oxygen （O） in the device.
The team is tackling two main questions: How do the chemical states of As （and neighboring atoms） evolve between initial deposition and post-activation? What stressors and processes enhance or prevent activation of As dopants?
University of Utah
University of Utah researchers will assess the role of microstructures in advanced CdTe devices. The goal is to improve the limiting open-circuit voltage while retaining the maximum values of short-circuit current and fill factor of CdTe solar cells by developing a novel architecture built on a comprehensive understanding of local carrier dynamics. The team plans to investigate the interfacial and microstructural characteristics of advanced CdTe （CdSe（1-x）Tex） Passivated Emitter and Rear Contact （PERC） solar cells.
A microcontact array platform with tunable pattern geometry will enable measurements of global （patterned CdTe PERC） and local carrier transport, delineating the contribution of grain bulk and grain boundaries to overall photovoltaic performance. Using complementary electron/optical microscopy, we will correlate the transport characteristics to the microstructural properties of each sample set （e.g., GrV-doped vs. copper （Cu）-doped CdTe PERCs）。
NREL will serve as a resource, support, and technical analysis center as the consortium develops a technology roadmap, conducts research to meet targets set within the roadmap, and regularly assesses the domestic CdTe supply chain for challenges and opportunities.
