Lattice Vibrations

Dresselhaus, M. S.; Dresselhaus, G.; Cronin, Stephen B.; Filho, A. G. Souza

doi:10.1007/978-3-662-55922-2_6

Cited by 5 publications

(10 citation statements)

References 1 publication

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“…Most notable is that ϵ 1 in the 50 mM PBTTT shows regimes where ϵ 1 0 (Figure b). Typically, metals have negative ϵ 1 values due to free carrier attenuation at frequencies less than the plasma frequency and a positive ϵ 1 at frequencies greater than the plasma frequency due to polarization . In contrast, Lorentz-like oscillators (e.g., band gap transitions) typically exhibit ϵ 1 > 0.…”

Section: Resultsmentioning

confidence: 55%

“…Here, we explore the use of SE to quantify the complex dielectric function in PBTTT, model the dielectric-like and metal-like contributions to the observable optical properties, and relate these contributions to the measurable thermoelectric properties and SLoT parameters. The complex dielectric function is expressed as where ϵ 1 (ω) is the real component, and ϵ 2 (ω) is the imaginary component . The complex dielectric function can link measurable optical properties, such as reflectivity, to the calculable material parameters, such as carrier densities.…”

Section: Resultsmentioning

confidence: 99%

“…SE measures the change in the ratio of the polarized light intensities (tan(ψ)) and phases (Δ) upon reflection, ,, and these changes in ψ and Δ are related to ϵ 1 (ω) and ϵ 2 (ω) through an optical model. Figure a shows representative ψ and Δ values for pristine PBTTT and 50 mM FeCl 3 doped PBTTT with comparable thicknesses, and Figure S13 shows ψ and Δ at each doping level.…”

Section: Resultsmentioning

confidence: 99%

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Quantifying Charge Carrier Localization in PBTTT Using Thermoelectric and Spectroscopic Techniques

et al. 2023

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Chemically doped poly[2,5-bis(3-alkylthiophen-2-yl)thieno[3,2-b]thiophene] (PBTTT) shows promise for many organic electronic applications, but rationalizing its charge transport properties is challenging because conjugated polymers are inhomogeneous, with convoluted optical and solid-state transport properties. Herein, we use the semilocalized transport (SLoT) model to quantify how the charge transport properties of PBTTT change as a function of iron(III) chloride (FeCl3) doping level. We use the SLoT model to calculate fundamental transport parameters, including the carrier density needed for metal-like electrical conductivities and the position of the Fermi energy level with respect to the transport edge. We then contextualize these parameters with other polymer-dopant systems and previous PBTTT reports. Additionally, we use grazing incidence wide-angle X-ray scattering and spectroscopic ellipsometry techniques to better characterize inhomogeneity in PBTTT. Our analyses indicate that PBTTT obtains high electrical conductivities due to its quickly rising reduced Fermi energy level, and this rise is afforded by its locally high carrier densities in highly ordered microdomains. Ultimately, this report sets a benchmark for comparing transport properties across polymer-dopant-processing systems.

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Section: Resultsmentioning

confidence: 55%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Quantifying Charge Carrier Localization in PBTTT Using Thermoelectric and Spectroscopic Techniques

et al. 2023

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“…For instance, the stronger the phonon–carrier interaction, the larger the n value. In classic crystalline semiconductors, the n value of 1.5 is an indication of an acoustic phonon, and larger than 1.5 is an indication of an optical phonon . However, the n index value is also dependent on nanostructure, temperature, etc.…”

Section: Resultsmentioning

confidence: 74%

Ultrafast Carrier Drift Transport Dynamics in CsPbI₃ Perovskite Nanocrystalline Thin Films

Kobbekaduwa,

Liu,

Zhao

et al. 2023

ACS Nano

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We study the early time carrier drift dynamics in CsPbI3 nanocrystal thin films with a sub 25 ps time resolution. Prior to trapping, carriers exhibit band-like transport characteristics, which is similar to those of traditional semiconductor solar absorbers including Si and GaAs due to optical phonon and carrier scattering at high temperatures. In contrast to the popular polaron scattering mechanism, the CsPbI3 nanocrystal thin film demonstrates the strongest optical phonon scattering mechanism among other inorganic–organic hybrid perovskites, Si, and GaAs. This ultrafast dynamics study establishes a foundation for understanding the fundamental carrier drift properties that drive perovskite nanocrystal optoelectronics.

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“…ϵ(ω) is a complex function expressed as ϵ(ω) = ϵ 1 (ω) + i ϵ 2 (ω) where ϵ 1 (ω) and ϵ 2 (ω) are real and imaginary parts. The imaginary part is calculated by a summation over empty bands as , where Ω and ϵ 0 are volume of the simulation cell and vacuum dielectric constant, respectively, ℏ ω and u . r are the energy of incoming radiation and momentum operator, respectively, and v and c symbolize valence and conduction bands, respectively.…”

Section: Resultsmentioning

confidence: 99%

Novel Metalless Chalcogen-Based Janus Layers: A Density Functional Theory Study

Vallinayagam,

Sudheer,

Aravindh

et al. 2023

J. Phys. Chem. C

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The electronic, thermodynamic, and optical properties of a new type of twodimensional Janus layer (JL) consisting exclusively of chalcogens are investigated using firstprinciples calculations. The permutations on atomic sites provide increased stability due to the multi-valency of chalcogens, and a heavier central atom further stabilizes the layer due to the increased coordination number. The investigated JLs are indirect bandgap materials with a bandgap larger than 1.23 eV, making them suitable for photocatalytic activity. Different feasible chemical potentials are analyzed, and chalcogens' poor limits are proposed to fabricate the JLs. Based on the comparison of the formation energy, the energetic profile of the JLs is identified as, irrespective of the chemical potentials of chalcogen. Hence, TeSeS is more stable than the JL arrangements SSeTe and SeSTe. The flat bands around the Fermi energy level and the reduction in path length between the maximum of conduction and minimum of valence bands explain the magnitude of multiple peaks observed in the optical spectra of the JLs. These absorptions turn the studied JLs into potential candidates for water splitting. The optimized bandgap reveals that the band edges efficiently straddle the water redox potentials at different pH levels. In addition, the positive vibrational frequencies depict the stability of these layers. Because of the minimal formation energy requirement, higher density of states around the Fermi level, as well as enhanced optical absorption compared to other JL, TeSeS JLs may lead to enhanced performance in photovoltaic and photocatalytic applications. These results add new members to the JL family of pure chalcogens and pave the way toward novel materials for respective applications.

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Lattice Vibrations

Cited by 5 publications

References 1 publication

Quantifying Charge Carrier Localization in PBTTT Using Thermoelectric and Spectroscopic Techniques

Quantifying Charge Carrier Localization in PBTTT Using Thermoelectric and Spectroscopic Techniques

Ultrafast Carrier Drift Transport Dynamics in CsPbI₃ Perovskite Nanocrystalline Thin Films

Novel Metalless Chalcogen-Based Janus Layers: A Density Functional Theory Study

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Lattice Vibrations

Cited by 5 publications

References 1 publication

Quantifying Charge Carrier Localization in PBTTT Using Thermoelectric and Spectroscopic Techniques

Quantifying Charge Carrier Localization in PBTTT Using Thermoelectric and Spectroscopic Techniques

Ultrafast Carrier Drift Transport Dynamics in CsPbI3 Perovskite Nanocrystalline Thin Films

Novel Metalless Chalcogen-Based Janus Layers: A Density Functional Theory Study

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Product

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Ultrafast Carrier Drift Transport Dynamics in CsPbI₃ Perovskite Nanocrystalline Thin Films