Effect of phonon confinement on photoluminescence from colloidal silicon nanostructures

Ghanta, Ujjwal; Ray, Mallar; Biswas, Samit; Sardar, Samim; Maji, Tuhin Kumar; Pal, Samir Kumar; Bandyopadhyay, Nil Ratan; Liu, Bo; Hossain, Syed Minhaz

doi:10.1016/j.jlumin.2018.04.052

Cited by 10 publications

(6 citation statements)

References 46 publications

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“…We hypothesize that these differences stem from sample homogeneity, size effects, defects, or strains (leading to broader distributions and peaks). However, there may be other explanations, such as different dielectric environments (dielectric screening affecting the exciton behavior), or surface/defect states that are more pronounced due to the high surface-to-volume ratio in colloidal samples. ,,,,− …”

Section: Resultsmentioning

confidence: 99%

Colloidal Synthesis of (PbBr₂)₂(AMTP)₂PbBr₄ a Periodic Perovskite “Heterostructured” Nanocrystal

Massasa,

Kortstee,

Lifer

et al. 2024

Crystal Growth & Design

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Heterostructures in nanoparticles challenge our common understanding of interfaces due to quantum confinement and size effects, giving rise to synergistic properties. An alternating heterostructure in which multiple and reoccurring interfaces appear in a single nanocrystal is hypothesized to accentuate such properties. We present a colloidal synthesis for perovskite layered heterostructure nanoparticles with a (PbBr 2 ) 2 (AMTP) 2 PbBr 4 composition. By varying the synthetic parameters, such as synthesis temperature, solvent, and selection of precursors, we control particle size, shape, and product priority. The structures are validated by X-ray and electron diffraction techniques. The heterostructure nanoparticles' main optical feature is a broad emission peak, showing the same range of wavelengths compared to the bulk sample.

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Section: Resultsmentioning

confidence: 99%

Colloidal Synthesis of (PbBr₂)₂(AMTP)₂PbBr₄ a Periodic Perovskite “Heterostructured” Nanocrystal

Massasa,

Kortstee,

Lifer

et al. 2024

Crystal Growth & Design

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“…This process becomes increasingly significant with enhanced phonon modes at higher temperatures. The recombination of free electron hole pairs can take place following excitonic dissociation, phonon assisted relaxation to the respective band edges [40,41,44] and finally, emission of photon with redshifted energy due to bandgap shrinkage effect. Hence, band assisted transition peak energies are expected to blueshift with increasing temperature at a rate determined by the degree of confinement followed by redshift beyond certain threshold temperature.…”

Section: Resultsmentioning

confidence: 99%

Temperature-dependent photoluminescence from nanostructured silicon: role of quantum confined band states and interfacial defects

Basu,

Ghanta,

Khan

et al. 2024

Preprint

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There are long-standing conflicting reports concerning the origin of strong visible photoluminescence (PL) observed in surface-oxidized nanostructured silicon. Though different competitive radiative recombination pathways involving intrinsic band states and oxide-related interfacial defects/traps mutually contribute to efficient PL emission, their individual role is still not well conceived. Temperature-dependent (\(5-350 K\)) PL measurements on nanostructured silicon with different crystallite size enable us to assign three distinct recombination channels comprising band-to-band, band-to-trap and trap-to-trap transitions to multiple emission bands appearing in the convoluted broad PL spectrum. At lower temperatures \((⪅ 225 K)\), the peaks originated from band-assisted transitions exhibit a nearly linear blue spectral shift following redshift at higher temperatures while the peak energy solely associated to trap involved transitions, increases monotonically almost at a constant rate throughout the experimental range of temperature. The temperature coefficients \(\alpha\) of the peak energy for the blue shifting region of the band-assisted transitions are found to show strong power law dependence \(\left( \alpha ={\alpha }_{0}+\frac{B}{{a}^{n}} \right)\) on the effective crystallite size \(\left(a\right)\)characterized by distinct values of the exponents\(\left(n\right)\). We have also presented a general analytical model for finite systems with separable pseudo-potential for obtaining carrier recombination dynamics within all possible recombination channels to assess their relative contribution in PL. The theoretical findings agree well with the experimentally obtained values of the power-law exponents\(\left(n\right)\). This study provides a novel approach to qualitatively differentiate between the radiative recombination channels involving quantum confined band-edge states and size independent defect states in nanostructured silicon.

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“…Moreover, the photocarriers live in those levels for a long time, since a very small attenuation of the PB signal is registered over time (see Figure 4 a and Figure A2 of the Appendix A ). In the case of SiNS, the former time scale is slower than the one expected for the relaxation time at the conduction band edge of the excited electrons through phonon (ph) emission in the case of bulk Si (of the order of fs to ps) because of the reduced amount of phonon modes due to the discretization of phonon density of states due to QC effects [ 32 ]. However, since the impinging photon flux is very high, it is reasonable to suppose a corresponding increase in the phonon number giving rise to an increase of e-ph scattering events which translates in a shortening of the relaxation time of the photoexcited electrons to the bottom of the conduction band.…”

Section: Resultsmentioning

confidence: 99%

Ultrafast Carrier Relaxation Dynamics in Quantum Confined Non-Isotropic Silicon Nanostructures Synthesized by an Inductively Coupled Plasma Process

et al. 2020

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To exploit the optoelectronic properties of silicon nanostructures (SiNS) in real devices, it is fundamental to study the ultrafast processes involving the photogenerated charges separation, migration and lifetime after the optical excitation. Ultrafast time-resolved optical measurements provide such information. In the present paper, we report on the relaxation dynamics of photogenerated charge-carriers in ultrafine SiNS synthesized by means of inductively-coupled-plasma process. The carriers’ transient regime was characterized in high fluence regime by using a tunable pump photon energy and a broadband probe pulse with a photon energy ranging from 1.2 eV to 2.8 eV while varying the energy of the pump photons and their polarization. The SiNS consist of Si nanospheres and nanowires (NW) with a crystalline core embedded in a SiOx outer-shell. The NW inner core presents different typologies: long silicon nanowires (SiNW) characterized by a continuous core (with diameters between 2 nm and 15 nm and up to a few microns long), NW with disconnected fragments of SiNW (each fragment with a length down to a few nanometers), NW with a “chaplet-like” core and NW with core consisting of disconnected spherical Si nanocrystals. Most of these SiNS are asymmetric in shape. Our results reveal a photoabsorption (PA) channel for pump and probe parallel polarizations with a maximum around 2.6 eV, which can be associated to non-isotropic ultra-small SiNS and ascribed either to (i) electron absorption driven by the probe from some intermediate mid-gap states toward some empty state above the bottom of the conduction band or (ii) the Drude-like free-carrier presence induced by the direct-gap transition in the their band structure. Moreover, we pointed up the existence of a broadband and long-living photobleaching (PB) in the 1.2–2.0 eV energy range with a maximum intensity around 1.35 eV which could be associated to some oxygen related defect states present at the Si/SiOx interface. On the other hand, this wide spectral energy PB can be also due to both silicon oxide band-tail recombination and small Si nanostructure excitonic transition.

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Effect of phonon confinement on photoluminescence from colloidal silicon nanostructures

Cited by 10 publications

References 46 publications

Colloidal Synthesis of (PbBr₂)₂(AMTP)₂PbBr₄ a Periodic Perovskite “Heterostructured” Nanocrystal

Colloidal Synthesis of (PbBr₂)₂(AMTP)₂PbBr₄ a Periodic Perovskite “Heterostructured” Nanocrystal

Temperature-dependent photoluminescence from nanostructured silicon: role of quantum confined band states and interfacial defects

Ultrafast Carrier Relaxation Dynamics in Quantum Confined Non-Isotropic Silicon Nanostructures Synthesized by an Inductively Coupled Plasma Process

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Effect of phonon confinement on photoluminescence from colloidal silicon nanostructures

Cited by 10 publications

References 46 publications

Colloidal Synthesis of (PbBr2)2(AMTP)2PbBr4 a Periodic Perovskite “Heterostructured” Nanocrystal

Colloidal Synthesis of (PbBr2)2(AMTP)2PbBr4 a Periodic Perovskite “Heterostructured” Nanocrystal

Temperature-dependent photoluminescence from nanostructured silicon: role of quantum confined band states and interfacial defects

Ultrafast Carrier Relaxation Dynamics in Quantum Confined Non-Isotropic Silicon Nanostructures Synthesized by an Inductively Coupled Plasma Process

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Colloidal Synthesis of (PbBr₂)₂(AMTP)₂PbBr₄ a Periodic Perovskite “Heterostructured” Nanocrystal

Colloidal Synthesis of (PbBr₂)₂(AMTP)₂PbBr₄ a Periodic Perovskite “Heterostructured” Nanocrystal