Scialog: Collaborative Teams
Awardee Profiles (2013)
Come see what's hot in science. RCSA's Awardee Profiles illustrates what leading scientists are discovering and teaching and how their work continues to shape our world. Additional awardee profiles can be found in the Awards Database.
Spectrum Splitting for Low-Cost Hybrid PV/Solar Thermal Generation
This team hopes to develop a hybrid low-concentration system that combines the high efficiency of Photovoltaics with the “dispatchability” of thermal storage. They envision a system which utilizes spectrum splitting, in which a molten salt receiver tube is transmissive in the visible and absorbing in the IR and UV. The IR and UV light heat the molten salt while the visible light is transmitted to a solar cell on the back side of the tube. In this manner, they plan on capturing the photons that would otherwise be unused by the solar cell, while also avoiding the loss of energy associated with thermalization of high-energy photons within the photovoltaic cell. Such a hybrid system may achieve both extremely high photoconversion efficiency and dispatchability. This approach results in two critical challenges: the development of an IR-opaque, visibly transparent, molten salt system (Lear) and the design (Bartl) and integration (Tamboli/Toberer) of a semicircular Bragg reactor into the solar concentrator. This project is co-funded by the Colorado Energy Research Collaboratory, a consortium of four public Colorado institutions. More
Targeting a New Product for Electrocatalytic CO2 Reduction: Formaldehyde
Baik and Trovitch propose to develop a new multi-component catalyst that will combine the electrocatalytic reduction of CO2 to CO with a metal-catalyzed hydrogenation to produce formaldehyde, thus partially mimicking the Fischer-Tropsch process without having to apply heat and high pressure. The catalyst consists of three functional fragments: (i) a CO-generator, (ii) a CO-polarizing activator, and (iii) a hydride donor. They aim to build upon the established electrocatalytic reduction of CO2 to give CO by installing a redox catalyst in close proximity that offers a metal hydride moiety. These two functionalities will react when facilitated by a charge-polarizing activator, such as a Ca2+ or Mg2+ cation, that will be presented to the metal bound carbonyl and engage in electrostatically induced charge polarization. More
Silicon Diselenide: A 1.7 eV Solar Absorber for Tandem Silicon Photovoltaics
Silicon is the photovoltaic market leader due to its high efficiency, low cost and proven reliability; currently it accounts for ~90% of PV shipments. Significant efficiency gains in this mature technology require radical approaches, such as tandem cell development. Detailed balance calculations by Tamboli and Toberer predict an efficiency gain of up to 12 percentage points by adding a 1.7 eV top cell to Si. However, the absence of an efficient top cell absorber remains a persistent technological challenge to the development of Si tandem cells. Candidates currently under consideration include dilute-nitride III-V materials, which are expensive and very difficult to grow, CZTS, which could damage the underlying Si cell because of the potential for Cu diffusion, and ZnSiP2, which is also under investigation by the PIs of this proposal.
Identification of a 1.7 eV-band gap material with good compatibility with Si would be transformative. More
Investigation into Interfacial States in Hybrid Polymer: Nanocrystal Solar Cells – Finding a Path to High Efficiencies
Organic photovoltaics (OPVs) are attractive candidates for third-generation solar cell technologies because they can be inexpensively solution processed (e.g., allowing roll-to-roll printing) in addition to being thin and flexible. The most commonly employed bulk heterojunction geometry consists of an active layer wherein a conjugated polymer donor is blended with a fullerene acceptor. Such types of OPVs have achieved power conversion efficiencies (PCEs) in excess of 7-8%; however, optimization of the donor component may be nearing its limit to further increase PCE, thereby suggesting the importance of exploring new acceptor types. Semiconductor nanocrystals possess several attributes that should make them attractive substitutes for fullerene acceptors; namely, (i) tunable band gaps and energy levels through compositional control and quantum confinement effects, (ii) strong, broad absorption at energies higher than the band edge, (iii) high dielectric constants to help overcome the strong exciton binding energy of conjugated polymers, and (iv) high electron mobilities relative to organic materials. More
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