Method for reducing point defect density in CZTS(e)
Publication Date: 2014-Aug-04
The IP.com Prior Art Database
Disclosed is a process for epitaxially growing Copper Zinc Tin Sulfo-selenide (CZT(S,Se)) on Silicon (Si) to suppress the formation of at least some types of point defects.
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Method for reducing point defect density in CZTS (
Copper Zinc Tin Sulfo-selenide (CZT(S,Se)) photovoltaic technology is limited by a low open-circuit voltage. A primary cause of this low open-circuit voltage is disorder in the CZTS material (i.e. a high density if point defects). An example point defect density (i.e. donor and acceptor defects) is approximately 10^19 per cubic centimeter. In contrast, Copper Indium Gallium Selenide (CIGS) photovoltaic materials have roughly 10^18 or less of these types of defects per cubic centimeter (estimated). The more severe band tailing in CZTS (caused by disorder) is closely correlated with lower open-circuit voltages.*
Healing these defects has a strong chance of improving the Voc of CZTS devices and is therefore of the utmost importance . A solution to this problem is not known.
The novel contribution is a process for epitaxially growing CZTS on Silicon (Si) to suppress the formation of at least some types of point defects . Having an epitaxial template and forcing the chemical species to assemble in accordance with the preferred orientation can reduce the site swapping that results in this band tailing behavior observed for polycrystalline CZTS. There are no other known methods for achieving such low point defect densities in CZTS.
The photoluminescence (PL) spectra measured at 4K sharpen for epitaxial (epi) materials, compared to polycrystalline materials, indicating a narrowing of the associated energetic dis...