Research - Thermal imaging and solar thermal energy harvesing devices

THERMAL IMAGING AND SOLAR THERMAL ENERGY HARVESTING DEVICES

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There has been always a strong motivation for development of high-performance thermal IR detectors that operate at room temperature so they can replace photon detectors that can only operate at cryogenic temperatures. Today, the manufacturing cost of a thermal IR imaging array is still considerably high and the performance is limited by the structure of the detector and more specifically by the heat transfer between the isolated sensitive area and the surroundings. With the new discovery of enhanced thermoelectric properties of silicon nanowire, it is highly desired to use them for device application. This is especially interesting for scale up as silicon electronic devices are still the most promising one for large scale application.

Achievements

Figure 1 shows an array of silicon based thermoelectric IR detector fabricated in our lab. Micromachined Si nanowire arrays are chip scale realization of a nanostructured device. In this device, there is no need for direct metal contact to the NWs that would significantly reduce the electrical contact resistance to the wires. For this, the NWs are fabricated in parallel and in similar size off from large Silicon pads that would provide the electrical connections. Si NWs have shown a significant enhancement in power conversion efficiency (Nature, Hochbaum et al, 451, January 2008). Moreover, Si NWs are compatible with CMOS fabrication technology. This makes them ideal for chip scale integrated IR imaging.

Representative Publications

1. A Method to Measure the Thermal Conductivity of Thermoelectric Nanowires, Nahida Akhter, Daryoosh Vashaee, IEEE Green Technologies Conference 2012 - Energy Generation & Storage Technologies, Tulsa, Oklahoma, April 19-20, 2012.

2. Planar Thin-Film Thermoelectric Solar Converters, Lobat Tayebi, Masoud Mozafari, Daryoosh Vashaee (under review).

Figure 1: SEM image of the focal plane array based on poly-silicon nanowire thermoelectrics.

O K L A H O M A S T A T E U N I V E R S I T Y

NanoScience and Engineering Research Group

Daryoosh Vashaee Phone: (918) 594-8017 Fax: (270) 897-1179 Email: daryoosh.vashaee@okstate.edu

Helmerich Advanced Technology Research Center 112-526 N Elgin Ave, Tulsa, Oklahoma 74106

We have filed a patent application on this technology. This work was supported by EDGE under subcontract with Amethyst Research Inc. The research is still ongoing. We have further extended this technology to planar solar thermoelectric convertors which can enable a new technology for solar energy harvesting.