Renormalization of excitonic properties by polar phonons

Abstract

We employ quasiparticle path integral molecular dynamics to study how theexcitonic properties of model semiconductors are altered by electron-phononcoupling. We describe ways within a path integral representation of the systemto evaluate the renormalized mass, binding energy, and radiative recombinationrate of excitons in the presence of a fluctuating lattice. To illustrate thisapproach, we consider Fr\"ohlich-type electron-phonon interactions and employan imaginary time influence functional to incorporate phonon-induced effectswithout approximation. The effective mass and binding energies are comparedwith perturbative and variational approaches, which provide qualitativelyconsistent trends. We evaluate electron-hole recombination rates as mediatedthrough both trap-assisted and bimolecular processes, developing a consistentstatistical mechanical approach valid in the reaction limited regime. Thesecalculations demonstrate how phonons screen electron-hole interactions,generically reducing exciton binding energies and increasing their radiativelifetimes.

Dynamic Quantum-State Renormalization and Effects of Competing Pathways on Carrier Relaxation in Semiconductor Nanoparticles

“…As mentioned above, this photoinduced increase in the effective masses of the carriers is observed and well modeled in monolayer TMDCs, although the band structure for those systems leads to an increase in the band gap energy. , Since the energies of the quantum-confinement states depend on the effective masses of the carriers, the quantum-confinement states in the VB and CB energetically shift with photoexcitation, even with the presence of only a single electron–hole pair in each NP, as depicted in Figure e. Photoexcited electrons, holes, and excitons may also interact with the ions in a polar semiconductor nanocrystal through Fröhlich interactions. − The photoexcited electron and hole interact with the cations and anions in the crystal lattice, perturbing the crystal structure and coupling with longitudinal optical (LO) phonons. − The changes in the crystal structure that result from these Fröhlich interactions result in contrasting electronic band structures and effective masses for the CB and VB in the unexcited and excited semiconductor NPs. − ,,− These energetic shifts are grouped together as QSR. Since the different quantum-confinement states have unique spatial probability densities, each state, including those that are occupied or not, should experience unique QSR that depend on the states in the VB and CB that are occupied. , As a result, the QSR of the quantum-confinement states should be dynamic, as the carriers relax through the energetically accessible states after photoexcitation.…”

Characterization of Enhanced Crystalline Structures of CdS Thin Films Deposited by Chemical Bath Deposition Caused by Doping with (Cu²⁺, Ag⁺, Au⁺) Transition Metal Ions

“…5, which could be related to S-S interactions of sulphur [46,48]. Additionally, an asymmetrical broadening of the 1LO mode to the low frequency side that can be attributed to confined phonons with frequencies centred around 260 cm -1 and overtones around 520 cm -1 that could be associated with CdS NPs [49][50][51]. The dislocation density that is defined as the length of dislocation lines per unit volume of the crystal.…”

Large and Small Polarons in Highly Efficient and Stable Organic‐Inorganic Lead Halide Perovskite Solar Cells: A Review

“…Furthermore, beads sharing the same index, originating from the electron or hole, interact through a fraction of Coulomb potential. [91] Analogous quasiparticle path integral methodologies have been employed to elucidate phenomena, such as photo-induced phase separation, [35,[92][93][94] charge trapping, [95] and charge recombination [96] in OIHPs. With this approach, an imaginary time influence functional can be derived, which facilitates the inclusion of dynamical and quantum mechanical effects of phonons within the confines of a harmonic approximation.…”