Low-cost “continuous flow” method for CIS

Researchers in the US and Korea have demonstrated feasibility to use continuous flow microreactors to produce thin-film absorbers for solar cells, a process they say is a promising low-cost alternative for thin-film PV manufacturing.


April 28, 2010 –
Researchers in the US and Korea have demonstrated feasibility to use continuous flow microreactors to produce thin-film absorbers for solar cells, a process they say is a promising low-cost alternative for thin-film PV manufacturing.

The work from Oregon State U. researchers, reported in Current Applied Physics, seeks to address several issues with the deposition of thin-film absorbers for solar cells such as copper indium diselenide (CIS). Previous approaches dependent upon sputtering, evaporation, and electrodeposition are time-consuming and/or require expensive vacuum systems or exotic chemicals, raising production costs. An alternative is a low-cost chemical bath deposition technique, normally performed as a batch process; however, thickness is difficult to control due to changes in the growth solution, and also is limited by depletion of reactants.

The technology developed by OSU assistant prof. Chih-hung Chang and collaborators at Yeungnam U. in Korea deposits nanostructure films on various surfaces in a continuous flow microreactor, which they say is a safer, faster, and more economical than other chemical solution approaches. “This system can produce thin-film solar absorbers on a glass substrate in a short time, and that’s quite significant,” a first for this technique, said Chang in a statement. Further work will focus on process control, testing the finished solar cell, improving efficiency to rival vacuum-based technology, and scaling the process to commercialization.

From the abstract
:

Polycrystalline CuInS2 thin films were deposited on glass substrates using a novel solution-based continuous flow microreactor process for the first time. A series of analysis was performed to characterize the CuInS2 thin films using UV-visible spectrophotometer, scanning electron microscope, X-ray diffraction spectrometer, and X-ray photoelectron spectroscopy. The estimated optical band gaps of CuInS2 thin films were in the range of 1.52-1.60 eV. The structural and chemical binding information indicated that CuInS2 thin films with a tetragonal chalcopyrite structure were successfully deposited. Dense film with a thickness around 1μm could be obtained with a 5min deposition time.

“If we could produce roofing products that cost-effectively produced solar energy at the same time, that would be a game changer,” Chang said. “All solar applications are ultimately a function of efficiency, cost and environmental safety, and these products might offer all of that.”

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