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Upconverter-Enhanced Molecular Photovoltaics: Towards Cost-Effective, Broadband Solar-Energy Conversion

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Jennifer Dionne and Michael McGehee, Materials Science and Engineering

The conversion efficiency of thin-film solar cells may be enhanced by adding upconverters, which allow more light from the sun to be absorbed by the solar cell. So far, the researchers have modeled how upconversion dyes could be used to improve the performance of the most common kinds of solar cells, including silicon, cadmium telluride, copper indium gallium diselenide, and dye-sensitized solar cells. These dyes convert low-energy photons to higher energy photons that can be utilized by the cell. The researchers find that coupling upconversion dyes with dye-sensitized solar cells is the most attractive option, because dye-sensitized cells have a larger band gap than other kinds of cells and can be made easily with two transparent electrodes. Initial calculations indicate that upconverting materials could improve these cell efficiencies by a few absolute percent.

The researchers have also developed a new process for depositing transparent electrodes on solid-state dye-sensitized solar cells that involves spraying silver nanowires. The researchers are using these silver nanowires and related metallic nanostructures to enhance the absorption and emission of upconverting materials, thereby improving their efficiency.

Meetings with other TomKat-funded teams working on solar research have been quite productive. The researchers were able to provide the team led by Chris Field with information on how various kinds of solar cells are affected by temperature and how their performance slowly degrades over time. Field is taking these factors into account when modeling how large-scale solar installations in the desert will perform. After several discussion with Stefan Reichelstein on the solar industry, Mike McGehee agreed to be a fellow at the Steyer-Taylor Center for Energy Policy & Finance. McGehee will provide the Steyer-Taylor Center with expertise on the science and technology of solar cells. Finally, the TomKat meetings have helped the researchers to improve a report they are preparing for George Schultz on the status of the solar industry and what research needs to be done to enable it to grow rapidly. Secretary Schultz incorporated the report into his presentation to policy makers in Washington, DC in 2014.

Publications and media

"Strain-induced modification of optical selection rules in lanthanide-based upconverting nanoparticles" Nano letters 15 (2015): 1891-1897.

"Photon upconversion with hot carriers in plasmonic systems" Applied Physics Letters 107 (2015): 1-4.

"Upconversion for enhanced photovoltaics" AIP Conference Proceedings 33 (2015): 33-43.

"Plasmon-enhanced upconversion" Journal of Physical Chemistry Letters 5 (2014): 4020-4031.

"Narrow-bandwidth solar upconversion: Case studies of existing systems and generalized fundamental limits" Journal of Applied Physics 113 (2013): 1-5.

"Spray deposition of silver nanowire electrodes for semitransparent solid-state dye-sensitized solar cells" Advanced Energy Materials 3 (2013) 1657-1663.

"Semi‐transparent polymer solar cells with excellent sub‐bandgap transmission for third generation photovoltaics" Advanced Materials 25 (2013): 7020-7026.

"Toward high-efficiency solar upconversion with plasmonic nanostructures" Journal of Optics 14 (2012): 1-7.

"Realistic upconverter-enhanced solar cells with non-ideal absorption and recombination efficiencies" Journal of Applied Physics 110 (2011): 1-9.         

Awarded 2011 as part of the TomKat's Large-Scale Solar project.