Enhanced p-Type Doping in Polycrystalline CdTe Films: Deposition and Activation

Journal Article · Wed Mar 20 00:00:00 EDT 2019 · IEEE Journal of Photovoltaics

DOI:https://doi.org/10.1109/JPHOTOV.2019.2902356· OSTI ID:1514851

McCandless, Brian ^[1]; Buchanan, Wayne ^[1]; Sriramagiri, Gowri ^[1]; Thompson, Christopher ^[1]; Duenow, Joel N. ^[2]; Albin, David S. ^[2]; Jensen, Soeren A. ^[2]; Moseley, John ^[2]; Al-Jassim, Mowafak M. ^[2]; Metzger, Wyatt K. ^[2]

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1. Univ. of Delaware, Newark, DE (United States)
2. National Renewable Energy Lab. (NREL), Golden, CO (United States)

An in situ nonequilibrium method to increase hole density in polycrystalline CdTe thin films to 10¹⁶ cm^-3 using group V substitution on Te is presented. Single-phase CdTe films doped with P, As, and Sb were deposited at 550 degrees C at 100-200 nm/s onto moving cadmium sulfide/high resistance transparent buffer layer/transparent conductive oxide /glass superstrates by vapor transport deposition in Cd overpressure from high purity compound sources. Doping levels before and after activation were determined by capacitance-voltage analysis of diagnostic devices. Secondary ion mass spectrometry depth profiling confirmed dopant incorporation levels of 10¹⁷ -10¹⁸ atoms/cm³ in as-deposited films. Electronic activation was carried out by post-deposition annealing in Cd or CdCl₂ vapor with fast cooling, increasing acceptor concentrations to >10¹⁵ cm^-3 for P and >10¹⁶ cm^-3 for As and Sb, compared with mid -10¹⁴ cm^-3 acceptor levels for undoped CdTe films. The activation methods are compatible with post-deposition processing presently used for high-efficiency CdTe solar cells. For the dopants As and Sb, the acceptor concentration increased by substitutional As Te and Sb Te formation, respectively, which was validated by cathodoluminescence spectroscopy.

• Research Organization: National Renewable Energy Lab. (NREL), Golden, CO (United States)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE)
• Grant/Contract Number: AC36-08GO28308
• OSTI ID: 1514851
• Report Number(s): NREL/JA-5K00-73937
• Journal Information: IEEE Journal of Photovoltaics, Vol. 9, Issue 3; ISSN 2156-3381
• Publisher: IEEE
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
36 MATERIALS SCIENCE
CdTe
doping
photovoltaic
thin film