Recombination and bandgap engineering in CdSeTe/CdTe solar cells

Journal Article · Mon Jul 22 00:00:00 EDT 2019 · APL Materials

DOI:https://doi.org/10.1063/1.5098459· OSTI ID:1547254

Zheng, Xin ^[1]; Kuciauskas, Darius  ^[2]; Moseley, John ^[2]; Colegrove, Eric M  ^[2]; Albin, David S ^[2]; Moutinho, Helio R ^[2]; Duenow, Joel N ^[2]; Ablekim, Tursunjan  ^[2]; Harvey, Steven P  ^[2]; Ferguson, Andrew J  ^[2]; Metzger, Wyatt K  ^[2]

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1. National Renewable Energy Laboratory (NREL), Golden, CO (United States); Univ. of Illinois, Chicago, IL (United States)
2. National Renewable Energy Laboratory (NREL), Golden, CO (United States)

Selenium compositional grading in CdTe-based thin-film solar cells substantively improves carrier lifetime and performance. However, where and how recombination lifetime improves has not been studied significantly. Here, we deposit a CdSe_xTe_1-x/CdTe bilayer on MgZnO/SnO₂/glass, which achieves a short-circuit current density greater than 28 mA/cm² and carrier lifetimes as long as 10-20 ns. We analyze the grain structure, composition, and recombination through the thickness of the absorber using electron backscatter diffraction, Auger-electron spectroscopy, cathodoluminescence spectrum imaging, and time-resolved photoluminescence microscopy. Despite small CdSeTe grains near the pn-junction and significantly larger CdTe grains in the rest of the film, both time-resolved photoluminescence and cathodoluminescence reveal that the carrier lifetime in CdSeTe alloy regions is longer than in CdTe regions. The results indicate that Se both passivates grain boundaries and improves grain-interior carrier lifetime. However, these effects occur only where there is significant alloying, which is important for bandgap engineering.

• Research Organization: National Renewable Energy Lab. (NREL), Golden, CO (United States)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE), Renewable Power Office. Solar Energy Technologies Office
• Grant/Contract Number: AC36-08GO28308
• OSTI ID: 1547254
• Report Number(s): NREL/JA-5K00-73619
• Journal Information: APL Materials, Vol. 7, Issue 7; ISSN 2166-532X
• Publisher: American Institute of Physics (AIP)
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
25 ENERGY STORAGE
auger electron spectroscopy
time-resolved photoluminescence
semiconductors
lifetime spectroscopy
cathodoluminescence spectroscopy
solar cells
interfaces
electron backscatter diffraction
spectral imaging
crystallographic defects