Potential-Induced Degradation of Cu(In,Ga)Se₂ Solar Cells: Alkali Metal Drift and Diffusion Effects

Journal Article · Mon Aug 06 00:00:00 EDT 2018 · IEEE Journal of Photovoltaics

DOI:https://doi.org/10.1109/JPHOTOV.2018.2858549· OSTI ID:1466561

Muzzillo, Christopher P. ^[1]; Glynn, Stephen ^[1]; Hacke, Peter ^[1]; Moutinho, Helio R. ^[1]; Young, Matthew R. ^[1]; Teeter, Glenn ^[1]; Repins, Ingrid L. ^[1]; Mansfield, Lorelle M. ^[1]

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1. National Renewable Energy Lab. (NREL), Golden, CO (United States)

Potential-induced degradation (PID) of photovoltaic modules is due to transport of alkali metal ions (Na⁺) from the soda-lime glass (SLG) into the semiconductors. For the most efficient polycrystalline absorbers, Na and K in the Cu(In,Ga)(Se,S)₂ (CIGS) absorber often benefit performance, so a more detailed mechanism for PID is needed. To that end, CIGS solar cells have been encapsulated, stressed with high voltage, and cored to extract the active regions for characterization. SLG substrates led to 14.9% efficiency on average, which reduced to 0% after 25 h of -1000 V bias. This was accompanied by increased Na in the CIGS layer, particularly at the buffer interface, as well as decreased carrier concentrations. On the other hand, borosilicate glass substrates with low Na and high K content led to 13.6% efficiency on average, which only reduced to 12.1% after 25 h of stress. This was accompanied by slightly increased K content in the CIGS layer. As K has led to recent world record efficiency CIGS devices, understanding Na and K similarities and differences may help to enhance initial efficiency and reduce PID.

• Research Organization: National Renewable Energy Lab. (NREL), Golden, CO (United States)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE), Solar Energy Technologies Office (EE-4S)
• Grant/Contract Number: AC36-08GO28308
• OSTI ID: 1466561
• Report Number(s): NREL/JA--5K00-71604
• Journal Information: IEEE Journal of Photovoltaics, Journal Name: IEEE Journal of Photovoltaics Journal Issue: 5 Vol. 8; ISSN 2156-3381
• Publisher: IEEE
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
36 MATERIALS SCIENCE
Cu(In
Ga)(Se
S)2 (CIGS)
alkali metal
encapsulation
potassium
potential-induced degradation (PID)
sodium