Impact of Self-Trapped Excitons on Blue Photoluminescence in TiO<sub>2</sub> Nanorods on Chemically Etched Si Pyramids

Saini, C. P.; Barman, A. Roy; Banerjee, Debosmita; Grynko, Oleksandr; Prucnal, S.; Gupta, Mukul; Phase, D. M.; Sinha, A. K.; Kanjilal, D.; Skorupa, W.; Kanjilal, A.

doi:10.1021/acs.jpcc.7b02218

Cited by 48 publications

(41 citation statements)

References 38 publications

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“…Emission band at 485 nm is ascribed to charge transfer from Ti 3+ to oxygen anion in a TiO 6 8− complex . All possible decay processes related to PL spectrum are illustrated in Scheme and are consistent with previous results …”

Section: Resultssupporting

confidence: 90%

Nb‐Dopant‐Induced Tuning of Optical and Electrical Property of Anatase TiO₂ Nanocrystals

et al. 2018

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For increasing demand of electrochromic smart window, flat panel display synthesis of high quality aliovalent doped wide bandgap semiconductor nanocrystals are gaining interest. In our manuscript we synthesized pure and Nb 5 + doped anatase TiO 2 nanocrystals by colloidal process. On increasing doping percentage size of TiO 2 nanoparticle was found to be decreased. Although pure TiO 2 nanocrystals are terminated with thermodynamically stable {101} facets but Nb 5 + doped TiO 2 was found to be terminated with high energy {103} facet by lowering the surface energy. Successful doping in anatase TiO 2 has been characterized by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance spectroscopy (EPR) analysis. Aliovalent dopant Nb 5 + generated free carriers in conduction band of TiO 2 . These free electrons results distinct plasmon absorption peak which appeared at wavelength of 1900 nm to 2700 nm. Plasmon peak found to be blue shifted with increase of dopant amount. Broad emission bands correspond to distinct transitions related to intermediate energy levels induced by oxygen vacancy. High colloidaly stable nanocrystals was deposited as crack free transparent conducting oxide thin film where we obtained very low sheet resistance with high optical transparency that leads to good figure of merit of thin film. Temperature driven metalinsulator transition for the lowest resistance film is explained by electron localization origination from random substitution of Nb into TiO 2 nanocrystals.

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Section: Resultssupporting

confidence: 90%

Nb‐Dopant‐Induced Tuning of Optical and Electrical Property of Anatase TiO₂ Nanocrystals

et al. 2018

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“…It is reported that the intrinsic transfer carriers in anatase can be excited with a light energy greater than 3.2 eV, which is consistent with the results shown in Figure b. Multiple PL signals in the blue‐light region centered at about 466 nm can be observed for all anatase TiO 2 samples; this can be attributed to localized defect states below the minimum of the conduction band (CB), such as V O s in the band gap . In this study, these defects can be assigned to lattice disorder and V O s located at the intergrain boundaries.…”

Section: Resultssupporting

confidence: 76%

“…These defect states, in general, are located below the lowest end of the CB at 0–1 eV, which can facilitate the transfer of carriers from these defect states to the CB . The green emission band at around 561 nm (2.21 eV) can be assigned to the recombination of trapped holes and oxygen molecules chemisorbed at V O s, or the recombination of electrons in the V O ‐related luminescence center to the holes in the valence band (VB), as confirmed by EPR spectroscopy (Figure S1 in the Supporting Information) . The EPR signal at g =2.005 can be attributed to surface defects, such as V O s with one positive charge .…”

Section: Resultsmentioning

confidence: 67%

Photocatalytic Properties Dependent on the Interfacial Defects of Intergrains within TiO₂ Mesocrystals

Wang

Chen

Luan

et al. 2018

Chemistry A European J

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The regulation of interfacial defects of nanocrystals aligned orderly in a superstructured photocatalyst is an effective approach to improve the photocatalytic performance. However, the synthesis of ordered self-assemblies with abundant interfacial defects and reactive sites is hard to achieve, and applications are limited due to the unclear physicochemical properties, which result from the unique mesocrystalline microstructures. It is reported herein that the photocatalytic properties depend on the interfacial defects of intergrains in anatase TiO mesocrystals (TMCs). Research reveals that the photocatalytic activity largely depends on defects, such as lattice distortion and oxygen vacancies, which are located at highly aligned interfaces of intergrains within TMCs. Moreover, the mesocrystalline TiO photocatalysts exhibit higher photocatalytic performance in organic degradation and hydrogen evolution, compared with single crystals and polycrystals; this can be ascribed to an appropriate amount of interfacial defects at the intergrains and improved carrier separation efficiency through the highly oriented interfaces. In addition, the photocatalytic performance of the TMCs could be further improved through regulation of defects by undergoing an annealing process under a redox atmosphere. This work can provide an avenue to defect engineering for improved photocatalytic performance.

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“…In contrast, the spectral shape of the normalized UV band attributed to STEs is virtually unchanged as evidenced from the invariance of the highenergy side of the UV peak with increasing temperature. The temperature independence of the spectral shape of the UV band is commonly observed for excitons immobilized by a local deformation of the crystal lattice because the energy of a STE emission critically depends on the distortion energy of self-trapped holes and is only weakly influenced by the bandedge energies [20,21]. The overall CL spectrum of Ga 2 O 3 is slightly redshifted from 3.45 eV at 10 K to 3.28 eV at 360 K due to the overlap with the enhanced BL emission relative to the UV peak.…”

Section: Resultsmentioning

confidence: 99%

Kinetics of charge carrier recombination in β−Ga2O3 crystals

Huynh

Lem

Kuramata³

et al. 2018

Phys. Rev. Materials

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Cathodoluminescence spectra were measured to determine the characteristics of luminescence bands and carrier dynamics in -Ga2O3 bulk single crystals. The CL emission was found to be dominated by a broad UV emission peaked at 3.40 eV, which exhibits strong quenching with increasing temperature; however, its spectral shape and energy position remain virtually unchanged. We observed a super-linear increase of CL intensity with excitation density; this kinetics of carrier recombination can be explained in terms of carrier trapping and charge transfer at Fe impurity centres. The temperature-dependent properties of this UV band are consistent with weakly bound electrons in self-trapped excitons with an activation energy of 48 ± 10 meV. In addition to the self-trapped exciton emission, a blue luminescence (BL) band is shown to be related to a donor-like defect, which increases significantly in concentration after hydrogen plasma annealing. The point defect responsible for the BL, likely an oxygen vacancy, is strongly coupled to the lattice exhibiting a Huang-Rhys factor of ~ 7.3.

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Impact of Self-Trapped Excitons on Blue Photoluminescence in TiO₂ Nanorods on Chemically Etched Si Pyramids

Cited by 48 publications

References 38 publications

Nb‐Dopant‐Induced Tuning of Optical and Electrical Property of Anatase TiO₂ Nanocrystals

Nb‐Dopant‐Induced Tuning of Optical and Electrical Property of Anatase TiO₂ Nanocrystals

Photocatalytic Properties Dependent on the Interfacial Defects of Intergrains within TiO₂ Mesocrystals

Kinetics of charge carrier recombination in β−Ga2O3 crystals

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Impact of Self-Trapped Excitons on Blue Photoluminescence in TiO2 Nanorods on Chemically Etched Si Pyramids

Cited by 48 publications

References 38 publications

Nb‐Dopant‐Induced Tuning of Optical and Electrical Property of Anatase TiO2 Nanocrystals

Nb‐Dopant‐Induced Tuning of Optical and Electrical Property of Anatase TiO2 Nanocrystals

Photocatalytic Properties Dependent on the Interfacial Defects of Intergrains within TiO2 Mesocrystals

Kinetics of charge carrier recombination in β−Ga2O3 crystals

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Impact of Self-Trapped Excitons on Blue Photoluminescence in TiO₂ Nanorods on Chemically Etched Si Pyramids

Nb‐Dopant‐Induced Tuning of Optical and Electrical Property of Anatase TiO₂ Nanocrystals

Nb‐Dopant‐Induced Tuning of Optical and Electrical Property of Anatase TiO₂ Nanocrystals

Photocatalytic Properties Dependent on the Interfacial Defects of Intergrains within TiO₂ Mesocrystals