CAREER: Using "hot" carriers for photovoltaics and photocatalysis

University Of Colorado At Boulder, Boulder CO

Investigators

Abstract

PI: Nagpal, Prashant Proposal Number: 1351281 Institution: University of Colorado at Boulder Title: CAREER: Using "hot" carriers for photovoltaics and photocatalysis This project focuses on development of nanostructured colloidal semiconductors for utilizing high energy quantum-confined states, or "hot-carriers", for improved photovoltaics and photodetection. The project will develop single and composite photocatalysts, with tuned energy levels, to generate wavelength-selective catalytic products for use as solar-fuels. While the cost of photovoltaic modules has reduced due to advances in thin-film semiconductor fabrication techniques, the energy mismatch of incident solar-radiation and finite-bandgap semiconductor leads to waste energy (>30% of incident radiation). This project will utilize this "excess energy" by using "hot-carriers" in quantum-confined nanostructured semiconductors, and by generating "wavelength-matched" selective solar fuels, without the need of expensive separations of high-value products. This can lead to development of so called "generation-III" photovoltaic and photocatalytic processes. This project will investigate charge and energy transport of "hot-carriers", in molecule-like quantum-confined energy levels of semiconductor nanocrystal colloids. Nominally, these hot-carriers cool down to bandedge, within a few picoseconds, making it difficult to develop charge transport devices, or hot-carrier devices. The PI will investigate a new class of molecular wires which can simultaneously transport hot-carriers and bandedge carriers, for efficient charge and energy transport, for applications in generation-III photovoltaics and photodetection devices. Besides these exciton-shelves, we will also explore nanocrystal superlattices for band-like transport of charges, and energy transfer complexes of donor-acceptor quantum dots, for development of novel devices and architectures. Towards generation of solar fuels, we will investigate applications of hot-carriers in quantum-confined semiconductor photocatalysts, for wavelength-selective generation of specific fuels. We will use CO2-H2O reduction and H2O-splitting as model systems, to demonstrate specific photocatalytic generation of high-value products, where the photon energy matches the reduction potential of the solar fuel produced. These generation-III photovoltaic and artificial photosynthetic processes will expand our knowledge of fundamental electronic phenomena following photogeneration of charge carriers, coupling between quantum states of semiconductor nanostructures and HOMO-LUMO level of molecular wires, and fundamental physics governing charge and energy transport in these semiconductor thin films. The study will also expand applications of these novel physical phenomena for renewable energy generation and development of next-generation devices and nanocatalysts. Besides development of novel devices for efficient photovoltaics and photocatalysis, the PI will promote awareness about research in renewable energy, and generate interest in K-12 students, particularly URM and women, to adopt careers in science and engineering education. The PI aims to develop a diverse team of trained engineers and scientists, and hence proposes new initiatives to reach these objectives.