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F.J. Pern,
L. Mansfield,
S. Glynn,
B. To, C. DeHart,
S. Nikumb,
C. Dinkel,
M. Rekow,
R. Murison,
T. Panarello,
C. Dunsky
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ABSTRACT: This paper describes the results from collaborative efforts in establishing an all-laser scribing technological capability for fabricating monolithically integrated CuInGaSe<sub>2</sub> (CIGS) mini-modules. The scribing parameters required for each of the three scribing steps (P1, P2, P3) were determined and optimized by using three specific samples fabricated at NREL. A fiber laser system using a single wavelength at 1064 nm was employed for the scribing, which allowed fine control of programmable pulse shape and pulse train. In general, the three scribe lines were clean and smooth. For the first time, two mini-modules, with an effective area of ~7-cm × 7-cm having 10 cell strips in series connection, were fabricated by the “all-laser-scribing” technology. Small-beam localized quantum efficiency (QE) analysis showed large non-uniformity across the cell arrays. Performance-degrading factors were investigated by photoluminescence (PL) and electroluminescence (EL) analysis. By increasing the ZnO:Al (AZO) thickness and re-scribing with P3, the two reworked mini-modules showed substantial improvements in efficiency (best at 8.3%) with a decrease in series resistance and an increase in shunt resistance and fill factor.
Photovoltaic Specialists Conference (PVSC), 2010 35th IEEE; 07/2010
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ABSTRACT: From our investigation of damp heat (DH)-induced degradation of the main component materials and complete CIGS devices in recent years, this paper summarizes the results on the (1) DH stability of several transparent conducting oxides deposited on glass substrates, including ZnO-based thin films, Sn-doped In<sub>2</sub>O<sub>3</sub> (ITO), and InZnO, and (2) effectiveness of physical and chemical mitigations for ZnO. The electrical results showed that the DH-induced degradation rates of i-ZnO, AZO, their bilayer (BZO), and Al-doped Zn<sub>1-x</sub>Mg<sub>x</sub>O are significantly greater than those of ITO and InZnO. Thicker AZO films are more stable than thinner ones. Structurally, upon DH exposures, the hexagonal ZnO-based thin films are transformed into highly resistive Zn(OH)<sub>2</sub> and/or cubic ZnO with increased transmittance and substantial morphological changes. In the physical mitigation approach, plasma-enhanced chemical vapor-deposited SiO<sub>x</sub>N<sub>y</sub> and sputter-deposited InZnO are employed separately as moisture barriers to protect the underlying i-ZnO, AZO, and/or BZO with good results. However, the SiO<sub>x</sub>N<sub>y</sub> films required working with chemical treatments to improve adhesion to the BZO surfaces. In the chemical mitigation method, simple wet-solution treatments using special formulations are found effective to protect BZO from DH attack.
Photovoltaic Specialists Conference (PVSC), 2010 35th IEEE; 07/2010
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ABSTRACT: The susceptibility of a thermally co-evaporated CuInGaSe<sub>2</sub> (CIGS) thin-film absorber to humidity and its consequence on composition, morphology, electrical and electronic properties, and device efficiency was investigated. CIGS films on Mo-coated soda lime glass were degraded either in the ambient at ~21°C and ~21% relative humidity (RH) for a period of several months or in damp heat (DH) at 85°C and 85% RH briefly for 15-30 min; then the films were processed simultaneously into devices in a batch that included an unexposed control. In addition to severe delamination on some samples of the absorber films, prolonged ambient exposure resulted in numerous ¿spot¿ formations that lost CIGS with scale-like disintegration rippling around the spots and showed a significant presence of Na. Exposure in DH for 5 h was able to reproduce the spot formations on the CIGS films. A significant to large decrease of cell efficiency was observed from 14%-16% for the unexposed control to 8%-11% for the CIGS absorber exposed in DH for 15 and 30 min and 1%-4%% for the ambient-degraded CIGS with high series resistance and very low shunt resistance.
Photovoltaic Specialists Conference (PVSC), 2009 34th IEEE; 07/2009
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R. Sundaramoorthy,
I.L. Repins,
T. Gennett,
F.J. Pern,
D. Albin,
J.V. Li, C. DeHart,
S. Glynn,
J.D. Perkins,
D.S. Ginley,
T. Gessert
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ABSTRACT: We investigated the optical and electrical properties of amorphous InZnO (IZO) as a potential replacement of Al-doped ZnO (AZO) conducting window layer for CuInGaSe<sub>2</sub> (CIGS) solar cells. The device performance of CIGS devices with IZO of different thickness and sheet resistance was compared with that of CIGS standard devices with AZO. The results show that the optical and electrical properties of IZO were affected by deposition conditions, especially by the oxygen concentration, and thickness. Initial results on the CIGS solar cells showed that devices with IZO yield cell efficiencies comparable to that of the devices with standard AZO, when the sheet resistance of IZO was close to that of AZO.
Photovoltaic Specialists Conference (PVSC), 2009 34th IEEE; 07/2009
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ABSTRACT: The stability of intrinsic and Al-doped single- and bi-layer ZnO for thin-film CuInGaSe2 solar cells, along with Al-doped Zn1-xMgxO alloy and Sn-doped In2O3 (ITO) and F-doped SnO2, was evaluated by direct exposure to damp heat (DH) at 85oC and 85% relative humidity. The results show that the DH-induced degradation rates followed the order of Al-doped ZnO and Zn1-xMgxO >> ITO > F:SnO2. The degradation rates of Al:ZnO were slower for films of higher thickness, higher substrate temperature in sputter-deposition, and with dry-out intervals. As inferred from the optical micro-imaging showing the initiation and propagation of degrading patterns and regions, the degradation behavior appears similar for all TCOs, despite the obvious difference in the degradation rate. A degradation mechanism is proposed to explain the temporal process involving thermal hydrolysis.
04/2008
