Interface reactions in CdTe solar cell processing
- National Renewable Energy Lab., Golden, CO (United States); and others
Currently, the best performing CdS/CdTe solar cells use a superstrate structure in which CdTe is deposited on a heated CdS/SnO{sub 2}/Glass substrate. In the close-spaced-sublimation (CSS) process, substrate temperatures in the range 550 C to 620 C are common. Understanding how these high processing temperatures impact reactions at the CdS/CdTe interface in addition to reactions between previously deposited layers is critical. At the SnO{sub 2}/CdS interface the authors have determined that SnO{sub 2} can be susceptible to reduction, particularly in H{sub 2} ambients. Room-temperature sputtered SnO{sub 2} shows the most susceptibility. In contrast, higher growth temperature chemical vapor deposited (CVD) SnO{sub 2} appears to be much more stable. Elimination of unstable SnO{sub 2} layers, and the substitution of thermal treatments for H{sub 2} anneals has produced total-area solar conversion efficiencies of 13.6% using non-optimized SnO{sub 2} substrates and chemical-bath deposited (CBD) CdS. Alloying and interdiffusion at the CdS/CdTe interface was studied using a new lift-off approach which allows enhanced compositional and structural analysis at the interface. Small-grained CdS, grown by a low-temperature CBD process, results in more CdTe{sub 1{minus}x}S{sub x} alloying (x = 12--13%) relative to larger-grained CdS grown by high-temperature CSS (x{approximately}2--3%). Interdiffusion of S and Te at the interface, measured with lift-off samples, appears to be inversely proportional to the amount of oxygen used during the CSS CdTe deposition. The highest efficiency to date using CSS-grown CdS is 10.7% and was accomplished by eliminating oxygen during the CdTe deposition.
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC36-83CH10093
- OSTI ID:
- 323666
- Report Number(s):
- CONF-971201-; TRN: IM9911%%280
- Resource Relation:
- Conference: 1997 fall meeting of the Materials Research Society, Boston, MA (United States), 1-5 Dec 1997; Other Information: PBD: 1998; Related Information: Is Part Of Thin-film structures for photovoltaics; Jones, E.D. [ed.] [Sandia National Labs., Albuquerque, NM (United States)]; Kalejs, J. [ed.] [ASE Americas Inc., Billerica, MA (United States)]; Noufi, R.; Sopori, B. [eds.] [National Renewable Energy Lab., Golden, CO (United States)]; PB: 325 p.; Materials Research Society symposium proceedings, Volume 485
- Country of Publication:
- United States
- Language:
- English
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