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Title: High-Efficiency Polycrystalline CdTe Thin-Film Solar Cells with an Oxygenated Amorphous CdS (a-CdS:O) Window Layer: Preprint

In the conventional CdS/CdTe device structure, the poly-CdS window layer has a bandgap of {approx}2.4 eV, which causes absorption in the short-wavelength region. Higher short-circuit current densities (Jsc) can be achieved by reducing the CdS thickness, but this can adversely impact device open-circuit voltage (Voc) and fill factor (FF). Also, poly-CdS film has about 10% lattice mismatch related to the CdTe film, which limits the improvement of device Voc and FF. In this paper, we report a novel window material: oxygenated amorphous CdS film (a-CdS:O) prepared at room temperature by rf sputtering. The a-CdS:O film has a higher optical bandgap (2.5-3.1 eV) than the poly-CdS film and an amorphous structure. The preliminary device results have demonstrated that Jsc of the CdTe device can be greatly improved while maintaining higher Voc and FF. We have fabricated a CdTe cell demonstrating an NREL-confirmed Jsc of 25.85 mA/cm2 and a total-area efficiency of 15.4%.
Authors:
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Publication Date:
OSTI Identifier:
15006968
Report Number(s):
NREL/CP-520-31429
TRN: US200412%%537
DOE Contract Number:
AC36-99-GO10337
Resource Type:
Conference
Resource Relation:
Conference: Conference title not supplied, Conference location not supplied, Conference dates not supplied; Other Information: PBD: 1 May 2002; Related Information: Prepared for the 29th IEEE PV Specialists Conference, 20-24 May
Research Org:
National Renewable Energy Lab., Golden, CO (US)
Sponsoring Org:
US Department of Energy (US)
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 36 MATERIALS SCIENCE; ABSORPTION; EFFICIENCY; FILL FACTORS; ORGANIC COMPOUNDS; SOLAR CELLS; SPUTTERING; THICKNESS; VOLATILE MATTER PV; OXYGENATED AMORPHOUS CDS; HIGH-EFFICIENCY POLYCRYSTALLINE; THIN-FILM SOLAR CELLS; SHORT-WAVELENGTH REGION; CADMIUM TELLURIDE (CDTE); PHOTOEMISSION SPECTROSCOPY (XPS); X-RAY DIFFRACTION; RAMAN SPECTRA; ATOMIC FORCE MICROSCOPY (AFM); SOLAR ENERGY - PHOTOVOLTAICS