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Proceedings Paper

Effects of rapid thermal processing and pulse-laser sintering on CdTe nanofilms for photovoltaic applications
Author(s): Kelly M. Rickey; Qiong Nian; Genqiang Zhang; Liangliang Chen; S. Venkataprasad Bhat; Yue Wu; Gary Cheng; Xiulin Ruan
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Paper Abstract

Effects of rapid thermal annealing (RTA) and dual compression-pulse-laser sintering (compression-PLS) on photovoltaic, CdTe nanowire (NW) and quantum dot (QD) films are investigated. Unlike regular furnace annealing, RTA involves raising the temperature of a substrate’s atmosphere by several hundred degrees in a matter of seconds, letting it sit for 30 to 120 seconds, then cooling it back to T0. To the best of our knowledge, such treatments of CdTe nanocrystal (NC) films have not been documented. In compression-PLS, a large pressure (MPa) is applied to a film through a laser-pulsing mechanism. Next, a high-energy, high frequency laser beam is pulsed onto it for sintering. During the compression, we used a single pulse of 5 nanoseconds. For the sintering, we used a 7.05 mJ beam for two pulses, at 25 ns per pulse. Such parameters were determined from SEM and other preliminary film characterization results. Morphology, material content, and conductivity of the films are analyzed before and after treatment using tunneling and scanning electron microscopy, EDS, and two-probe measurements, respectively. This study provides new knowledge regarding the morphological and structural outcomes of RTA and compression-PLS on CdTe nanoparticle films. Furthermore, RTA and compression-PLS can increase the film electrical conductivity by improving their contact with each other. We found that RTA partially sinters the film and enhances inplane current density by a factor of ~1.7, for a values on the order of ~10-7A/cm2. Compression-PLS successfully sinters the NW film and improves current density up to a factor of ~167, for values on the order of ~10-5 A/cm2. On the other hand, QD films do not exhibit current density improvement with treatments. These values remain on the order of ~10-7 A/cm2. The resistivities of the sintered NW films reach as low as 6.7*106 Ω*cm, while the RTA’d NW film has a resistivity on the order of 108 Ω*cm. These values are comparable to values of bulk and thin-film CdTe: single crystalline, undoped CdTe resistivity values range from 105 to 108 Ω*cm,8,9 while polycrystalline thin-film values range from 104 to 106 Ω*cm.11,12 The QD films also have comparable resistivities to these results, albeit on the higher side.

Paper Details

Date Published: 17 October 2012
PDF: 11 pages
Proc. SPIE 8465, Nanostructured Thin Films V, 846505 (17 October 2012); doi: 10.1117/12.929965
Show Author Affiliations
Kelly M. Rickey, Purdue Univ. (United States)
Qiong Nian, Purdue Univ. (United States)
Genqiang Zhang, Purdue Univ. (United States)
Liangliang Chen, Purdue Univ. (United States)
S. Venkataprasad Bhat, Purdue Univ. (United States)
Yue Wu, Purdue Univ. (United States)
Gary Cheng, Purdue Univ. (United States)
Xiulin Ruan, Purdue Univ. (United States)


Published in SPIE Proceedings Vol. 8465:
Nanostructured Thin Films V
Tom G. Mackay; Yi-Jun Jen; Raúl J. Martín-Palma, Editor(s)

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