Influence of thermal annealing on the structural and optical properties of CdSe nanoparticles

Farva, Umme; Park, Chinho

doi:10.1016/j.solmat.2009.10.003

Cited by 46 publications

(44 citation statements)

References 33 publications

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“…[24] It is known [25] that small nanocrystals carry a large number of defects, most likely because the relatively short reaction time does not allow thermal annealing. [26] It should also be considered that the fraction of surface atoms on the total number of atoms is higher for small particles. When the growth occurs in the focusing regime, [14,15] as for mid-sized particles, it can be hypothesized that some correction of surface defects takes place besides the narrowing of the size distribution.…”

Section: Absorption and Luminescence Propertiesmentioning

confidence: 99%

Structural and Size Effects on the Spectroscopic and Redox Properties of CdSe Nanocrystals in Solution: The Role of Defect States

et al. 2011

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Two series of CdSe quantum dots (QDs) with different diameters are prepared, according to frequently used protocols of the same synthetic procedure. For each sample the photophysical properties and the potentials for the first reduction and oxidation processes in organic solution are determined. The band gap obtained from electrochemical experiments is compared with that determined from the absorption and luminescence spectra. While the optical band gap decreases upon increasing the nanocrystal diameter, as expected on the basis of quantum confinement, the redox potentials and the electrochemical band gap are not monotonously related to the QD size. For both series, the smallest and largest QDs are both easier to oxidize and reduce than mid-sized QDs. In fact, the latter samples exhibit very broad voltammetric profiles, which suggests that the heterogeneous electron-transfer processes from/to the electrode are kinetically hindered. Conversely, the electrochemical band gap for the smallest and largest particles of each series is somewhat smaller than the optical band gap. These results indicate that, while the optical band gap depends on the actual electron-hole recombination within the nanocrystal, and therefore follows the size dependence expected from the particle-in-a-box model, the electrochemical processes of these QDs are strongly affected by other factors, such as the presence of surface defects. The investigations suggest that the influence of these defects on the potential values is more important for the smallest and largest QDs of each series, as confirmed by the respective luminescence bands and quantum yields. An interpretation for the size-dependent evolution of the surface defects in these nanocrystals is proposed based on the mechanism of their formation and growth.

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Section: Absorption and Luminescence Propertiesmentioning

confidence: 99%

Structural and Size Effects on the Spectroscopic and Redox Properties of CdSe Nanocrystals in Solution: The Role of Defect States

et al. 2011

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“…After being cleaned, the substrate was treated with N 2 plasma in a barrel-type plasma chamber for 10 min at a power of 50 W and a pressure of 200 mTorr. The PEDOT: PSS layer was spin-coated on the plasma-treated substrate with a typical thickness of 100 nm and vacuum-dried at 100 o C [16].…”

Section: July 2011mentioning

confidence: 99%

Controlling the morphology of trioctyl phosphine oxide-coated cadmium selenide/poly 3-hexyl thiophene composite active layer for bulk hetero-junction solar cells

Truong

Monroe

Farva

et al. 2011

Korean J. Chem. Eng.

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Bulk hetero-junction solar cells with CdSe nanoparticles-P 3 HT (poly 3-hexyl thiophene) composite active layer were fabricated, and the control of morphological feature of the nanoparticle-polymer composite thin films was investigated. A binary solvent composed of a primary solvent with intermediate polarity and a secondary solvent with high polarity was found to be effective in controlling the dispersion of the CdSe nanocrystals in the P 3 HT matrix, and the modification of the nanocrystal surface by liquid-liquid extraction process was found to be effective in achieving the desired composite film morphology. Surface roughness of the active layer was optimized for various loadings of CdSe nanoparticles and could be reproducibly controlled to less than 10 nm.

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“…Since a colloidal route for the synthesis of high-quality CdSe quantum dots (QDs) was first developed in 1993 [8], the synthesis and characterization of CdSe nanocrystals were investigated intensively [8][9][10][11][12][13]. In the colloidal route synthesis of CdSe QDs, CdO dissolved in tri-n-octyl phosphine oxide (TOPO) and tri-n-octyl phosphine selenide (TOPSe) are typically used as the starting materials.…”

Section: Introductionmentioning

confidence: 99%

“…For large-scale application as in thin film solar cell, the size controllability and device-level quality control of CdSe QDs are very important. For these purposes, non-TOP-based liquids such as paraffin, pyridine and dodecylamine (DDA) are sometimes employed to substitute TOPO with a new surface ligand, in an attempt to bring improved optical properties and band edge photoluminescence (PL) of CdSe QDs [10][11][12][13]. A recent study on bulk hetero-junction (BHJ) solar cells made with CdSe nanocrystals embedded in P 3 HT polymer showed that, using pyridine-capped CdSe, the solar cell efficiency was improved as much as two-fold compared with that of original TOPO-capped CdSe BHJ solar cells at the otherwise same fabrication conditions, and the result was mainly attributed to the enhanced current collection [14].…”

Section: Introductionmentioning

confidence: 99%

“…In this work, TOPO-capped CdSe nanocrystals were synthesized by slightly modified Peng and Peng's method [8,9,13], and pyridine-capped CdSe were obtained from the corresponding TOPO-capped CdSe by exchange of TOPO with pyridine using liquid-liquid extraction process. The structural and optical properties of TOPO-and pyridine-capped CdSe were characterized by various analysis methods including X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), PL and time-resolved PL (TRPL) spectroscopy.…”

Section: Introductionmentioning

confidence: 99%

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Synthesis and characterization of CdSe nanocrystals capped with TOPO and pyridine

Luo

Farva

Truong

et al. 2012

Journal of Crystal Growth

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Influence of thermal annealing on the structural and optical properties of CdSe nanoparticles

Cited by 46 publications

References 33 publications

Structural and Size Effects on the Spectroscopic and Redox Properties of CdSe Nanocrystals in Solution: The Role of Defect States

Structural and Size Effects on the Spectroscopic and Redox Properties of CdSe Nanocrystals in Solution: The Role of Defect States

Controlling the morphology of trioctyl phosphine oxide-coated cadmium selenide/poly 3-hexyl thiophene composite active layer for bulk hetero-junction solar cells

Synthesis and characterization of CdSe nanocrystals capped with TOPO and pyridine

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