Thursday, December 24, 2009

With Microwave Methods, Taiwanese Researchers Quickly Fabricate Nano-Scale Chalcopyritic Powders to Make Improved Solar Cells


Industrial Technology Research Institute (Hsinchu County, TW) scientists Yu Huang,  Bing-Joe Hwang,  Hsuan-Fu Wang, Chih-Chung Wu and Shih-Hong Chang developed fast fabrication methods for nano-scale chalcopyritic powders and polymeric thin-film solar cells.  The researchers devised a solvothermal synthesis methods for polynary chalcopyritic powders enhanced by microwave heating which improves the purity of the resulting powders. The reaction time is shortened and production cost is reduced. The nano-scale chalcopyritic powders are applicable to polymeric thin-film solar cells.

According to U.S. Patent Application 20090317939, the fabrication method for nano-scale chalcopyritic powders includes providing a solution consisting of group IB, IIIA, VIA elements on the chemistry periodic table or combinations thereof. The solution is heated by a microwave generator. The solution is washed and filtered by a washing agent. The solution is subsequently dried, thereby acquiring nano-scale chalcopyritic powders. 

Fabrication processes for forming a copper arsenide (indium) diselenide absorption thin film are chiefly divided into vacuum processes and non-vacuum processes. The vacuum processes include co-evaporation, and selenization, while the non-vacuum processes include spray pyrolysis, electro-deposition, and paste coating. With aspect to powder synthesis, high-energy mechanical alloying and solo-thermal methods are most popular.  The main drawback of the conventional solution synthesis of the copper arsenide (indium) diselenide nano-scale powders and other nano-scale chalcopyritic powders is that it is time consuming. Nano chalcopyritic powder processing can take three to four days by conventional means.

In order to solve the time consuming issues of the conventional solvothermal synthesis methods for nano-scale chalcopyritic powders, Industrial Technology Research Institute scientists provide microwave enhanced heating to shorten solvothermal reaction time to synthesis copper indium diselenide, copper arsenide diselenide, and copper arsenide indium diselenide nano-scale powders and nano-scale chalcopyritic copper gallium diselenide (CuGaSe2) powders.  All can be synthesized with shortened reaction times.

The Industrial Technology Research Institute invention is advantageous in that microwave heating can effectively and efficiently reduce reaction time of solvothermal synthesis of the chalcopyritic structure powders. Since microwave heating transfers and provides thermal energy to substances via electromagnetic field which can rapidly penetrate substances and reduce thermal gradients, both reaction time and energy consumption are desirably reduced. Additionally, most polar compounds can consequently rotate due to induction by microwave electromagnetic field, and ions solved in the solution can simultaneously migrate with high speed vibration induced by microwave electromagnetic field. Thus, reaction is accelerated due to the collision probability increment between the adjacent molecules.

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