Dynamics of photoexcited carrier relaxation and recombination in CdTe/CdS thin films
Efficiency-limiting defects in photovoltaic devices are readily probed by time-resolved spectroscopy. This paper presents the first direct optical measurements of the relaxation and recombination pathways of photoexcited carriers in the CdS window layer of CdTe/CdS polycrystalline thin films. Femtosecond time-resolved pump/probe measurements indicate the possible existence of a two-phase CdS/CdSTe layer, rather than a continuously graded alloy layer at the CdTe/CdS interface. Complementary time-resolved photoluminescence (PL) measurements show that the photoexcited carriers are rapidly captured by deep-level defects. The temporal and density-dependent properties of the photoluminescence prove that the large Stokes shift of the PL relative to the band edge is due to strong phonon coupling to deep-level defects in CdS. The authors suggest that modifications in the CdS processing may enhance carrier collection efficiency in the blue spectral region.
- Publication Date:
- OSTI Identifier:
- Report Number(s):
- NREL/TP--410-21091; CONF-960513--
ON: DE96007880; TRN: 96:006561-0017
- Resource Type:
- Resource Relation:
- Conference: 25. photovoltaic solar energy conference, Washington, DC (United States), 13-17 May 1996; Other Information: PBD: May 1996; Related Information: Is Part Of NREL preprints for the photovoltaic specialists conference of IEEE twenty-five; Gwinner, D. [ed.]; PB: 172 p.
- Research Org:
- National Renewable Energy Lab., Golden, CO (United States)
- Country of Publication:
- United States
- 14 SOLAR ENERGY; CADMIUM TELLURIDES; CHARGE CARRIERS; CADMIUM SULFIDES; SOLAR CELLS; RELAXATION LOSSES; RECOMBINATION; THIN FILMS
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