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Title: Properties of reactively sputtered oxygenated cadmium sulfide (CdS:O) and their impact on CdTe solar cell performance

Oxygenated cadmium sulfide (CdS:O) is commonly used as the n-type window layer in high-performance CdTe heterojunction solar cells. This layer is deposited by reactive sputtering, but the optimal amount of oxygen in the sputtering ambient is highly dependent on the specific system and process employed. In this work, the intrinsic properties of CdS:O were measured as a function of the oxygen content (0%–10%) in the sputtering ambient and correlated to device performance with the goal of better defining optimal CdS:O properties for CdTe solar cells. Optimal performance was found using CdS:O films that contained ∼40 at. % oxygen as measured by Rutherford backscattering spectrometry. X-ray photoelectron spectroscopy confirmed these results and showed that oxygen is incorporated primarily as oxygenated sulfur compounds (SO{sub x}). Device efficiency improved from 10.5% using CdS to >14% with CdS:O due largely to increases in short-circuit current density as well as a modest improvement in open-circuit voltage. The transparency of the CdS:O films was well correlated with observed improvements in blue quantum efficiency with increasing oxygen content. The optical bandgap of as-deposited CdS:O was identified as a simple metric for process optimization and transfer, with 2.8 eV being ideal for the device architecture employed.
Authors:
;  [1] ;  [2] ; ; ; ; ; ;  [3]
  1. Chemical and Biological Engineering Department, Colorado School of Mines, 1613 Illinois St., Golden, Colorado 80401 (United States)
  2. Department of Physics, Colorado School of Mines, 1523 Illinois St., Golden, Colorado 80401 (United States)
  3. National Renewable Energy Laboratory, 15013 Denver West Pkwy., Golden, Colorado 80401 (United States)
Publication Date:
OSTI Identifier:
22392134
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Vacuum Science and Technology. A, Vacuum, Surfaces and Films; Journal Volume: 33; Journal Issue: 2; Other Information: (c) 2014 American Vacuum Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; CADMIUM SULFIDES; CADMIUM TELLURIDES; CURRENT DENSITY; DEPOSITS; ELECTRIC POTENTIAL; ELECTRICAL FAULTS; HETEROJUNCTIONS; OXYGEN; PERFORMANCE; QUANTUM EFFICIENCY; RUTHERFORD BACKSCATTERING SPECTROSCOPY; SOLAR CELLS; SPUTTERING; X-RAY PHOTOELECTRON SPECTROSCOPY