Synthesis of Ligand-Stabilized Silicon Nanocrystals with Size-Dependent Photoluminescence Spanning Visible to Near-Infrared Wavelengths

Hessel, Colin M.; Reid, Dariya K.; Panthani, Matthew G.; Rasch, Michael; Goodfellow, Brian W.; Wei, Junwei; Fujii, Hiromasa; Akhavan, Vahid A.; Korgel, Brian A.

doi:10.1021/cm2032866

Cited by 339 publications

(584 citation statements)

References 55 publications

(129 reference statements)

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“…1.6 Observed photoluminescence from nanocrystalline silicon 9,21,30,56 In these studies, decreases in the Si NP diameter are concurrent with increased PL energies, which supports QC theory. 9,21,30,52,56 However, even though QCbased PL has been reported for H-Si NPs, the Si-H bond is known to be thermodynamically weak relative to other Si-X bonds (X = O, N, F, etc.)…”

Section: Quantum Confinement In Silicon Nanoparticlessupporting

confidence: 67%

“…6,9 The salient feature of each of these equations is the dependence of E g on the inverse square of the nanoparticle diameter. Equation 1 is one version of the EMA, which was adapted by Hessel et al,9 that summarizes the relationship between particle diameter (d) and E g :…”

Section: Quantum Confinement In Silicon Nanoparticlesmentioning

confidence: 99%

“…9,21,30,52,56 However, even though QCbased PL has been reported for H-Si NPs, the Si-H bond is known to be thermodynamically weak relative to other Si-X bonds (X = O, N, F, etc.) and therefore it is expected to be unstable in experimental and ambient conditions.…”

Section: Quantum Confinement In Silicon Nanoparticlesmentioning

confidence: 99%

“…Most chemical modifications made to the H-Si NP surface, with the exception of alkyl-passivation, 9 are reported to introduce electronically active defect states into the electronic structure that can reduce the radiative yield of interband transitions. For example, oxidation of high surface area Si occurs readily in ambient and laboratory conditions and is frequently cited to coincide with sudden, drastic changes in the observed PL.…”

Section: Effect Of Defects On Photoluminescence From Silicon Nanopartmentioning

confidence: 99%

“…Furthermore, the bandgap energy (E g ) is expected to be dependent on the size of the crystallite domains and therefore tunable. [6][7][8][9] The size-dependence of the optical properties of Si on the nanometer length scale heighten the potential for the development of all Si-based optoelectronic devices in which signals would be transferred by photopulses (i.e., light) generated by the nanocrystalline Si diodes. [10][11][12][13] Currently, the development of this type of technology is largely limited by the low efficiency and instability of the PL of Si nanomaterials.…”

Section: General Introductionmentioning

confidence: 99%

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Investigation into Effects of Instability and Reactivity of Hydride-Passivated Silicon Nanoparticles on Interband Photoluminescence

Radlinger¹

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While silicon has long been utilized for its electronic properties, its use as an optical material has largely been limited due to the poor efficiency of interband transitions. However, discovery of visible photoluminescence (PL) from nanocrystalline silicon in 1990 triggered many ensuing research efforts to optimize PL from nanocrystalline silicon for optical applications. Currently, use of photoluminescent silicon nanoparticles (Si NPs) is commercially limited by: 1) the instability of the energy and intensity of the PL, and 2) the low quantum yield of interband PL from Si NPs.Herein, red-emitting, hydrogen-passivated silicon nanoparticles (H-Si NPs) were synthesized by thermally-induced disproportionation of a HSiCl 3 -derived (HSiO 1.5 )n polymer. The H-Si NPs produced by this method were then subjected to various chemical and physical environments to assess the long-term stability of the optical properties as a function of changing surface composition. This dissertation is intended to elucidate correlations between the reported PL instability and the observed changes in the Si NP surface chemistry over time and as a function of environment.First, the stability of the H-Si NP surface at slightly elevated temperatures towards reactivity with a simple alkane was probed. The H-Si NPs were observed by FT-IR spectroscopy to undergo partial hydrosilylation upon heating in refluxing hexane, in addition to varying degrees of surface oxidation. The unexpected reactivity of the Si surface in n-hexane supports the unstable nature of the H-Si NP surface, and furthermore implicates the presence of highly-reactive Si radicals on the surfaces of the Si NPs. We propose that reaction of alkene impurities with the Si surface radicals is largely responsible for the observed surface alkylation. However, we also present an alternate ii mechanism by which Si surface radicals could react with alkanes to result in alkylation of the surface.Next, the energy and intensity stability of the interband PL from H-Si NPs in the presence of a radical trap was probed. Upon addition of (2,2,6,6,-tetramethyl-piperidin-1-yl)oxyl (TEMPO), the energy and intensity of the interband transition was observed to change over time, dependent on the reaction conditions. First, when the reaction occurred at 4ºC with minimal light exposure, the interband transition exhibited a gradual hypsochromic shift to between 595 nm and 655 nm, versus the λ max of the original low energy emission peak at 700 nm, depending on the amount of TEMPO in the sample.Second, when the reaction proceeded at room temperature with frequent exposure to 360 nm irradiation, the original interband transition at 660 nm was quenched while a new peak at 575 nm developed. Based on all the data collected and analyzed, we assign the 595 -655 nm transition as due to interband exciton recombination from Si NPs with reduced diameters relative to the original Si NPs. We furthermore assign the 575 nm transition as due to an oxide-related defect state resulting from rapid oxidation of pho...

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