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Proceedings Paper

Sub-bandgap laser annealing of room temperature deposited polycrystalline CdTe
Author(s): Brian J. Simonds; Sudhajit Misra; Naba Paudel; Koen Vandewal; Alberto Salleo; Christos Ferekides; Michael A. Scarpulla
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Paper Abstract

We investigate how post-deposition laser annealing can be used to improve structural and electronic quality of room-temperature deposited CdTe. We use continuous-wave, 1064 nm laser light to anneal CdTe solar cell stacks prior to back contact deposition. Sub-bandgap optical absorption measurements by photothermal deflection spectroscopy show a reduction of sub-bandgap defects due to the annealing process. Since the 1064 nm light is only partially absorbed, in situ monitoring of the transmitted light during laser annealing gives real-time information about changes in the material. These results reveal an evolution of electronic defect annealing and surface roughness modification with laser exposure time. This hypothesis is supported by electron microscopy. Two distinct annealing regimes emerge: one at low laser power where electronic defect annealing saturates after about one minute exposure and another at high power where structural defects are annealed after several minutes exposure. Temperatures reached during laser annealing are estimated by finite element modeling of the thermal transport due to heat generation from optical absorption.

Paper Details

Date Published: 8 October 2014
PDF: 6 pages
Proc. SPIE 9180, Laser Processing and Fabrication for Solar, Displays, and Optoelectronic Devices III, 91800F (8 October 2014); doi: 10.1117/12.2062178
Show Author Affiliations
Brian J. Simonds, The Univ. of Utah (United States)
Sudhajit Misra, The Univ. of Utah (United States)
Naba Paudel, The Univ. of Toledo (United States)
Koen Vandewal, Stanford Univ. (United States)
Alberto Salleo, Stanford Univ. (United States)
Christos Ferekides, Univ. of South Florida (United States)
Michael A. Scarpulla, The Univ. of Utah (United States)

Published in SPIE Proceedings Vol. 9180:
Laser Processing and Fabrication for Solar, Displays, and Optoelectronic Devices III
Edward W. Reutzel, Editor(s)

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