Open AccessIdentifying the Electronic Properties Relevant to Improving the Performance of High Band-Gap Copper Based I-III-VI2 Chalcopyrite Thin Film Photovoltaic Devices: Final Subcontract Report, 27 April 2004-15 September 2007
Author(s) -
J. David Cohen
Publication year - 2008
Language(s) - English
Resource type - Reports
DOI - 10.2172/937345
Subject(s) - chalcopyrite , band gap , materials science , optoelectronics , photocurrent , photovoltaic system , copper indium gallium selenide solar cells , capacitance , thin film , copper , solar cell , analytical chemistry (journal) , electrode , electrical engineering , nanotechnology , metallurgy , chemistry , engineering , chromatography
This report summarizes the development and evaluation of higher-bandgap absorbers in the CIS alloy system. The major effort focused on exploring suitable absorbers with significant sulfur alloying in collaboration with Shafarman's group at the Institute of Energy Conversion. Three series of samples were examined; first, a series of quaternary CuIn(SeS)2-based devices without Ga; second, a series of devices with pentenary Cu(InGa)(SeS)2 absorbers in which the Se-to-S and In-to-Ga ratios were chosen to keep the bandgap nearly constant, near 1.52 eV. Third, based on the most-promising samples in those two series, we examined a series of devices with pentenary Cu(InGa)(SeS)2 absorbers with roughly 25 at.% S/(Se+S) ratios and varying Ga fractions. We also characterized electronic properties of several wide-bandgap CuGaSe2 devices from both IEC and NREL. The electronic properties of these absorbers were examined using admittance spectroscopy, drive-level capacitance profiling, transient photocapacitance, and transient photocurrent optical spectroscopies. The sample devices whose absorbers had Ga fraction below 40 at.% and S fractions above 20 at.% but below 40% exhibited the best electronic properties and device performance