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Prasun K. Mandal - One of the best experts on this subject based on the ideXlab platform.
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Extent of Shallow/Deep Trap States beyond the Conduction Band Minimum in Defect-Tolerant CsPbBr3 Perovskite Quantum Dot: Control over the Degree of Charge Carrier Recombination.
The journal of physical chemistry letters, 2020Co-Authors: Saptarshi Mandal, Soumen Mukherjee, Debjit Roy, Swarnali Ghosh, Prasun K. MandalAbstract:Perovskite quantum dots (PQDs) are known to be defect-tolerant, possessing a clean Band gap with optically inactive benign defect states. However, we show that there exist significant deep trap states beyond the Conduction Band Minimum, although the extent of shallow trap states is observed to be minimal. The extent of deep trap states beyond the Conduction Band Minimum seems to be significant in PQDs; however, the extent is less than that of even optically robust CdSe- and InP-based core/alloy-shell QDs. In-depth analyses based on ultrafast transient absorption and ultrasensitive single-particle spectroscopic investigations decode the underlying degree of charge carrier recombination in CsPbBr3 PQDs, which is quite important for energy applications.
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extent of shallow deep trap states beyond the Conduction Band Minimum in defect tolerant cspbbr3 perovskite quantum dot control over the degree of charge carrier recombination
Journal of Physical Chemistry Letters, 2020Co-Authors: Saptarshi Mandal, Soumen Mukherjee, Debjit Roy, Swarnali Ghosh, Prasun K. MandalAbstract:Perovskite quantum dots (PQDs) are known to be defect-tolerant, possessing a clean Band gap with optically inactive benign defect states. However, we show that there exist significant deep trap states beyond the Conduction Band Minimum, although the extent of shallow trap states is observed to be minimal. The extent of deep trap states beyond the Conduction Band Minimum seems to be significant in PQDs; however, the extent is less than that of even optically robust CdSe- and InP-based core/alloy-shell QDs. In-depth analyses based on ultrafast transient absorption and ultrasensitive single-particle spectroscopic investigations decode the underlying degree of charge carrier recombination in CsPbBr3 PQDs, which is quite important for energy applications.
Alex Zunger - One of the best experts on this subject based on the ideXlab platform.
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quantum size induced electronic transitions in quantum dots indirect Band gap gaas
Physical Review B, 2008Co-Authors: Junwei Luo, Alberto Franceschetti, Alex ZungerAbstract:We discuss the physical origin of the previously predicted quantum-size-induced electronic transitions in spherical GaAs quantum dots. By using atomistic pseudopotential calculations for freestanding GaAs dots and for GaAs dots embedded in an AlGaAs matrix, we are able to distinguish two types of direct/indirect transitions: (i) in freestanding GaAs dots, the Conduction-Band Minimum changes from $\ensuremath{\Gamma}$-like to $X$-like as the radius of the dot is reduced below 1.6 nm, leading to a direct/indirect transition in reciprocal space. (ii) In GaAs dots embedded in AlAs, the Conduction-Band Minimum changes from dot localized to barrier localized as the radius of the dot is reduced below 4.2 nm, corresponding to a direct-to-indirect transition in real space.
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L-to-X crossover in the Conduction-Band Minimum of Ge quantum dots
Physical Review B, 2000Co-Authors: F. A. Reboredo, Alex ZungerAbstract:Screened-pseudopotential calculations of large ((less-or-similar sign)3000 atoms) surface-passivated Ge quantum dots show that below a critical dot diameter that depends on the passivant, the character of the lowest Conduction state changes from an L-derived to an X-derived state. Thus, in this size regime, Ge dots are Si-like. This explains the absence, in a pseudopotential description, of a crossing between the Band gaps of Si and Ge dots as a function of size, predicted earlier in single-valley effective-mass calculations. The predicted L{yields}X crossing suggests that small Ge dots will have an X-like, red shift of the Band gap with applied pressure, as opposed to an L-like blue shift of large dots. (c) 2000 The American Physical Society.
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Prediction of a strain-induced Conduction-Band Minimum in embedded quantum dots
Physical Review B, 1998Co-Authors: Andrew J. Williamson, Alex Zunger, Andrew CanningAbstract:Free-standing InP quantum dots have previously been theoretically and experimentally shown to have a direct Band gap across a large range of experimentally accessible sizes. We demonstrated that when these dots are embedded coherently within a GaP barrier material, the effects of quantum confinement in conjunction with coherent strain suggest there will be a critical diameter of dot ({approx}60 {Angstrom}), above which the dot is direct, type I, and below which it is indirect, type II. However, the strain in the system acts to produce another Conduction state with an even lower energy, in which electrons are localized in small pockets at the interface between the InP dot and the GaP barrier. Since this Conduction state is GaP X{sub 1c} derived and the highest occupied valence state is InP, {Gamma} derived, the fundamental transition is predicted to be indirect in both real and reciprocal space ({open_quotes}type II{close_quotes}) for all dot sizes. This effect is peculiar to the strained dot, and is absent in the freestanding dot. {copyright} {ital 1998} {ital The American Physical Society}
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identity of the Conduction Band Minimum in alas 1 gaas 1 001 superlattices intermixing induced reversal of states
Physical Review B, 1992Co-Authors: D B Laks, Alex ZungerAbstract:First-principles pseudopotential calculations on the (001) (AlAs){sub 1}/(GaAs){sub 1} superlattice (SL) shows that {ital partial} intermixing of the Al and Ga atoms relative to the abrupt case lowers its formation energy, making this SL even stabler at low {ital T} than the fully randomized Al{sub 0.5}Ga{sub 0.5}As alloy. Concomitantly, the Conduction-Band Minimum (CBM) reverts from the GaAs {ital L}-derived state, to the {ital X}{sup {ital x}{ital y}}-derived AlAs state. The previously noted discrepancy between theory (pertinent to abrupt SL's and yielding an {ital L}-derived CBM) and experiment (yielding an {ital X}{sup {ital x}{ital y}}-derived CBM) is therefore attributed to insufficient interfacial abruptness in the samples used to date in experimental studies.
Saptarshi Mandal - One of the best experts on this subject based on the ideXlab platform.
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Extent of Shallow/Deep Trap States beyond the Conduction Band Minimum in Defect-Tolerant CsPbBr3 Perovskite Quantum Dot: Control over the Degree of Charge Carrier Recombination.
The journal of physical chemistry letters, 2020Co-Authors: Saptarshi Mandal, Soumen Mukherjee, Debjit Roy, Swarnali Ghosh, Prasun K. MandalAbstract:Perovskite quantum dots (PQDs) are known to be defect-tolerant, possessing a clean Band gap with optically inactive benign defect states. However, we show that there exist significant deep trap states beyond the Conduction Band Minimum, although the extent of shallow trap states is observed to be minimal. The extent of deep trap states beyond the Conduction Band Minimum seems to be significant in PQDs; however, the extent is less than that of even optically robust CdSe- and InP-based core/alloy-shell QDs. In-depth analyses based on ultrafast transient absorption and ultrasensitive single-particle spectroscopic investigations decode the underlying degree of charge carrier recombination in CsPbBr3 PQDs, which is quite important for energy applications.
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extent of shallow deep trap states beyond the Conduction Band Minimum in defect tolerant cspbbr3 perovskite quantum dot control over the degree of charge carrier recombination
Journal of Physical Chemistry Letters, 2020Co-Authors: Saptarshi Mandal, Soumen Mukherjee, Debjit Roy, Swarnali Ghosh, Prasun K. MandalAbstract:Perovskite quantum dots (PQDs) are known to be defect-tolerant, possessing a clean Band gap with optically inactive benign defect states. However, we show that there exist significant deep trap states beyond the Conduction Band Minimum, although the extent of shallow trap states is observed to be minimal. The extent of deep trap states beyond the Conduction Band Minimum seems to be significant in PQDs; however, the extent is less than that of even optically robust CdSe- and InP-based core/alloy-shell QDs. In-depth analyses based on ultrafast transient absorption and ultrasensitive single-particle spectroscopic investigations decode the underlying degree of charge carrier recombination in CsPbBr3 PQDs, which is quite important for energy applications.
K W West - One of the best experts on this subject based on the ideXlab platform.
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Space group symmetry of the Conduction Band Minimum in very short period superlattices
Solid State Communications, 1992Co-Authors: W D Schmidt, M D Sturge, Loren Pfeiffer, K W WestAbstract:Abstract In a perfect (GaAs) m (AlAs) n type-II superlattice the symmetry of the Conduction Band states, and therefore the Band mixing, depends on whether m, n or (m+n) are odd or even. We have investigated the symmetry of the Conduction Band minima in very short-period superlattices (m≤n≤4) by time resolved photoluminescence under applied uniaxial stress, and find that selection rules that depend on space group symmetry through k-conservation are well obeyed, but parity with respect to space inversion is apparently not a good quantum number in our samples.
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Conduction Band Minimum of gaas 1 alas 1 superlattices relationship to x Minimum of alas
Physical Review B, 1991Co-Authors: Weikun Ge, W D Schmidt, M D Sturge, L N Pfeiffer, K W WestAbstract:We show that the Conduction-Band Minimum in a (GaAs){sub 1}/(AlAs){sub 1} superlattice derives from the {ital X}{sub {ital x},}{ital y} Minimum of bulk AlAs, not from {ital L} of GaAs as predicted by many theoretical calculations. This is shown by the sign of the shift in the low-temperature photoluminescence under (001) stress, by the relative magnitudes of the shifts under (100) and (110) stress, by the phonon sideBands, and by the observation of a splitting under (100) but not under (110) stress.
Swarnali Ghosh - One of the best experts on this subject based on the ideXlab platform.
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Extent of Shallow/Deep Trap States beyond the Conduction Band Minimum in Defect-Tolerant CsPbBr3 Perovskite Quantum Dot: Control over the Degree of Charge Carrier Recombination.
The journal of physical chemistry letters, 2020Co-Authors: Saptarshi Mandal, Soumen Mukherjee, Debjit Roy, Swarnali Ghosh, Prasun K. MandalAbstract:Perovskite quantum dots (PQDs) are known to be defect-tolerant, possessing a clean Band gap with optically inactive benign defect states. However, we show that there exist significant deep trap states beyond the Conduction Band Minimum, although the extent of shallow trap states is observed to be minimal. The extent of deep trap states beyond the Conduction Band Minimum seems to be significant in PQDs; however, the extent is less than that of even optically robust CdSe- and InP-based core/alloy-shell QDs. In-depth analyses based on ultrafast transient absorption and ultrasensitive single-particle spectroscopic investigations decode the underlying degree of charge carrier recombination in CsPbBr3 PQDs, which is quite important for energy applications.
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extent of shallow deep trap states beyond the Conduction Band Minimum in defect tolerant cspbbr3 perovskite quantum dot control over the degree of charge carrier recombination
Journal of Physical Chemistry Letters, 2020Co-Authors: Saptarshi Mandal, Soumen Mukherjee, Debjit Roy, Swarnali Ghosh, Prasun K. MandalAbstract:Perovskite quantum dots (PQDs) are known to be defect-tolerant, possessing a clean Band gap with optically inactive benign defect states. However, we show that there exist significant deep trap states beyond the Conduction Band Minimum, although the extent of shallow trap states is observed to be minimal. The extent of deep trap states beyond the Conduction Band Minimum seems to be significant in PQDs; however, the extent is less than that of even optically robust CdSe- and InP-based core/alloy-shell QDs. In-depth analyses based on ultrafast transient absorption and ultrasensitive single-particle spectroscopic investigations decode the underlying degree of charge carrier recombination in CsPbBr3 PQDs, which is quite important for energy applications.