DocumentCode :
3519475
Title :
Synthesis and characterization of PECVD-grown, silane-terminated silicon quantum dots
Author :
Anderson, Ingrid E. ; Shircliff, Rebecca A. ; Simonds, Brian ; Stradins, Pauls ; Taylor, P. Craig ; Collins, Reuben T.
Author_Institution :
Colorado Sch. of Mines, Golden, CO, USA
fYear :
2012
fDate :
3-8 June 2012
Abstract :
Semiconductor quantum dots (QDs) have been the subject of intense research interest due to novel experimentally observed properties, such as tunable bandgap, phonon bottleneck, and a variety of surface effects. The control of these properties makes quantum dots a candidate for revolutionizing a variety of fields, including photovoltaics. Because silicon is such a well characterized PV material in its bulk form, it would be a good choice for QD research for application in solar cells. In addition, there is recent theoretical evidence that its indirect gap may become more direct as size decreases, allowing for a fine-tuning of the absorption characteristics for photovoltaics. We present a method for grafting silanes onto low-temperature-plasma synthesized silicon quantum dots. The resulting solution of dots is characterized with Fourier transform infrared spectroscopy and transmission electron microscopy, and determined to be a colloidal suspension. The silane is attached at a single point on the quantum dot surface to avoid cross-linking and multilayer formation, and photoluminescence spectroscopy shows the colloidal suspension of dots is stable for over two months in air. The hydroxyl-terminated surfaces required for silanization are created by wet chemical etch, which can be used to tune the luminescence of the silicon dots in the green- to red-wavelength range. Unpassivated Si quantum dots show vastly different behaviors in electron paramagnetic resonance than wet-chemically oxidized, silane-functionalized particles. The dangling bond density of unpassivated Si quantum dots is large and changes over time, while the dangling bond density of the silanized dots is unchanged and undetectable. This suggests silanized dots will be better for solution-processed PV devices since transport will not be hindered by dangling bonds. Finally, we perform PL excitation (PLE) spectroscopy on both ensembles of dots, and discuss the way such spectra are represented in the literatur- , especially in comparison with absorption. This discussion is critical to the success of Si QDs in optoelectronic devices, since absorption and luminescence play critical roles.
Keywords :
Fourier transform spectra; absorption; colloids; dangling bonds; elemental semiconductors; etching; infrared spectra; luminescence; photoluminescence; plasma CVD; semiconductor growth; semiconductor quantum dots; silicon; solar cells; suspensions; transmission electron microscopy; Fourier transform infrared spectroscopy; PECVD-grown synthesis; PL excitation spectroscopy; PLE spectroscopy; absorption characteristics; characterized PV material; colloidal suspension; dangling bond density; electron paramagnetic resonance; hydroxyl-terminated surfaces; low-temperature-plasma synthesized silicon quantum dots; luminescence; multilayer formation; optoelectronic devices; phonon bottleneck; photoluminescence spectroscopy; photovoltaic cell; quantum dot surface; semiconductor quantum dots; silane-terminated silicon quantum dots; solar cells; solution-processed PV devices; surface effects; transmission electron microscopy; tunable bandgap; wet chemical etch; wet-chemically oxidized silane-functionalized particles; Absorption; Nanocrystals; Quantum dots; Silicon; Spectroscopy; Surface treatment; nanocrystals; optoelectronic devices; paramagnetic resonance; photoluminescence; silicon;
fLanguage :
English
Publisher :
ieee
Conference_Titel :
Photovoltaic Specialists Conference (PVSC), 2012 38th IEEE
Conference_Location :
Austin, TX
ISSN :
0160-8371
Print_ISBN :
978-1-4673-0064-3
Type :
conf
DOI :
10.1109/PVSC.2012.6317962
Filename :
6317962
Link To Document :
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