Solar To Electric Power Generation

Photovoltaics (PV) or solar cells directly convert the energy from the sun, called photons, to electricity. Some of the sun's photons are absorbed by the solar cell's active material (which is a semiconductor) and that energy is transferred to electrons. The electrons move in the material to become current, which than can be extracted as electricity from the cell. To learn more about photovoltaics, visit the Department of Energy's Solar Energy Technologies Program website.

Solar cells can be made from a wide range of semiconductor materials, with the dominate material today being silicon (Si) and cadmium telluride (CdTe). The CfSE research highlighted below is studying new materials and device designs that can move today's technology to higher efficiencies with lower cost of manufacturing.

Quantum Dot Solar Cells

Solar cells based on neat films of electronically-coupled PbSe nanocrystals sandwiched between two electrodes are excellent model systems for studying junction formation, dynamics and charge transport in quantum dot solids. Moreover, these devices are promising for efficient, low-cost solar energy conversion because they can be processed in solution and may produce photocurrent that is enhanced by multiple exciton generation (MEG).

(a) A cartoon of the PbSe nanocrystal Schottky solar cell. Light is incident through the glass. (b) The device stack in cross section, showing the thickness and schematic roughness of each layer.

PbSe nanocrystal cells were recently shown to yield large short-circuit current densities and power conversion efficiencies above 4%. Our efforts focus on improving the efficiency and stability of this new class of devices and to demonstrate MEG-enhanced device performance with very high efficiencies (>35%).

Thin Film Solar Cells Made With Sustainable Materials

Fundamental to solving our energy problems is the discover of new materials that can effectively harness the sun's energy but are based on abundant and non-toxic elements. Current research is focused on the synthesis of thin films, nanocrystals, and nanowires made from sustainable materials using mulitple synthetic techniques.

Relative abundance of minable elements. The CfSE research is focusing on the "rock-forming elements." Source: USGS

Metal-Semiconductor Hybrid Nanowires Utilizing Plasmonics for Concentrating Solar Radiation

New nanofabrication capabilities have opened the door to studying the fundamentals of solar energy conversion with new nanoarchitectures. Atomic steps on the surface of highly ordered pyrolytic graphite can be used to nucleate silver or gold nanoparticles. During deposition, metal adatoms incident on the graphite surface diffuse laterally until encountering a step edge and aggolomerating with other metal atoms to form a metal nucleus. With techniques that study the surface of the materials, CfSE researchers study how the metal’s surface plasmons affect the properties of semiconductors. Plasmons can localize incident light and enhance solar light absorption, therefore having the ability to increase the efficiency of ultra-thin solar cells.

Electron microscopy images at different scales of silver nano-particle arrays on a graphite substrate grown at 400 ºC deposition temperature with 5.5 nanometer mass thickness of silver.

Center Funded Publications