Luminescence of direct-and indirect-gap electron-hole plasma in TlBr

Kohlová, V.; Pelant, I.; Hála, J.; Ambroz, M.; Vacek, K.

doi:10.1016/0038-1098(87)91122-7

Cited by 10 publications

(5 citation statements)

References 15 publications

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“…Figure A shows UV‐vis absorbance spectra of TlBr nanocrystals and Figure B shows diffuse reflectance measurements of dried Tl 2 AgBr 3 nanocrystal powder. The TlBr nanocrystals have an absorption edge at 405 nm (3.06 eV), close to the reported bulk optical gap of 3.0 eV . Bulk TlBr also has a parity‐forbidden indirect transition at 2.6–2.7 eV, but there is no evidence of this feature in the absorbance spectra of the nanocrystals.…”

Section: Resultssupporting

confidence: 62%

“…The TlBr nanocrystals have an absorption edge at 405 nm (3.06 eV), close to the reported bulk optical gap of 3.0 eV . Bulk TlBr also has a parity‐forbidden indirect transition at 2.6–2.7 eV, but there is no evidence of this feature in the absorbance spectra of the nanocrystals. For the the Tl 2 AgBr 3 nanocrystals, an extrapolation of the linear region of the Kubelka Munk function in Figure B reveals an indirect bandgap of 3.1 eV .…”

Section: Resultssupporting

confidence: 62%

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Synthesis of TlBr and Tl₂AgBr₃ Nanocrystals

et al. 2020

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There are only a few examples of nanocrystal synthesis with thallium (Tl). Here, we report the synthesis of uniform, ligand-stabilized colloidal nanocrystals of TlBr and Tl 2 AgBr 3 nanocrystals with average diameter ranging between 10 and 20 nm. TlBr nanocrystals are made by hot injection of trimethylsilyl bromide (TMSBr) into solutions of oleylamine, oleic acid and octadecene with thallium (III) or thallium (I) acetate. Tl 2 AgBr 3 nanocrystals form when silver (I) acetate is included in the reaction. The TlBr nanocrystals have CsCl crystal structure with a direct band gap of 3.1 eV. The Tl 2 AgBr 3 nanocrystals have trigonal dolomite crystal structure with an indirect band gap of 3.1 eV. The TlBr nanocrystals made with thallium (III) were sufficiently uniform to assemble into face-centered cubic (fcc) superlattices.[a] Dr.

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Section: Resultssupporting

confidence: 62%

Section: Resultssupporting

confidence: 62%

Synthesis of TlBr and Tl₂AgBr₃ Nanocrystals

et al. 2020

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“…On the other hand, P-band emission has been observed in 3D perovskites only, where the density of states near the polariton (photon-like exciton) bottleneck is nonzero for inelastic exciton–exciton scattering . In fact, a thin 3D perovskite can be sandwiched by high-reflectivity mirrors to form a microcavity structure to induce strong coupling between excitons and cavity photons, yielding half-matter/half-light quasi-particles known as cavity polaritons that can undergo Bose–Einstein condensation or lasing even at room temperature. , Although electron–hole plasma (EHP) is a well-established phase composed of uncorrelated electrons and holes in conventional semiconductors, , to the best of our knowledge, no clear spectroscopic evidence for EHP has been reported from the family of 3D halide perovskites. Instead, a rather exotic phase of correlated electron–hole pairs, so-called Mahan excitons, has been quite recently reported in MAPbBr 3 , which can exist even above the Mott density with no clear signature for EHP …”

Section: Introductionmentioning

confidence: 99%

Role of the A-Site Cation in Low-Temperature Optical Behaviors of APbBr₃ (A = Cs, CH₃NH₃)

et al. 2021

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APbBr3 (A = Cs, CH3NH3) are prototype halide perovskites having bandgaps of 2.30–2.35 eV at room temperature, rendering their apparent color nearly identical (bright orange but opaque). Upon optical excitation, they emit bright photoluminescence (PL) arising from carrier recombination whose spectral features are also similar. At 10 K, however, the apparent color of CsPbBr3 becomes transparent yellow, whereas that of CH3NH3PbBr3 does not change significantly due to the presence of an indirect Rashba gap. With increasing the excitation level, evolution of the PL spectra, which are excitonic at 10 K, reveals the emergence of P-band emission arising from inelastic exciton–exciton scattering. Based on the spectral location of the P-band, exciton binding energies are determined to be 21.6 ± 2.0 and 38.3 ± 3.0 meV for CsPbBr3 and CH3NH3PbBr3, respectively. Intriguingly, upon further increase in the exciton density, electron–hole plasma appears in CsPbBr3 as evidenced by both red-shift and broadening of the PL. This phase, however, does not occur in CH3NH3PbBr3 presumably due to polaronic effects. Although the A-site cation is believed not to directly impact optical properties of APbBr3, our results underscore its critical role, which destines different high-density phases and apparent color at low temperatures.

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“…However, we note that a similar effect might be expected for the indirect bandedge measurements, but was not observed, since both the low temperature and room temperature bandgaps are consistent with other reported values. Finally, it is possible that the higher energy emission is associated with electron-hole plasma (EHP) emission, 24 although studies of the temperature dependence of EHP emission in GaAs show it following the bandgap variation. 25 Further studies will be required as a function of excitation energy on the 3.0 eV emission peak.…”

Section: Analytical Modeling and Discussionmentioning

confidence: 99%