Chalcopyrite Semiconductors

The structure of CuInSe2 is shown on the right. CuInSe2 is a rather unique material in that its near bandedge absorption is one of the highest known among semiconductors.  This and the fact that even in its polycrystalline form non-radiative recombination centers can be strongly suppressed has lead to the use of CuInSe2 and its alloys Cu(Ga,In)(S,Se)2 to be employed in photovoltaic applications.  Another interesting attribute of these chalcopyrite compounds is that they are not line compounds and for deviations from the ideal stoichiometric composition, both structural and optical changes manifest themselves. We are striving to both understand these changes from a fundamental point of view (structural changes, point defect types and concentrations), but also seeking to apply this understanding for the optimal design of chalcopyrite based photovoltaics. To this end we are growing both CuInSe2 and CuGaSe2 using molecular beam epitaxy for fundamental materials characterization.  We are also fabricating photovoltaics using polycrystalline material grown using co-evaporation.

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