Text Box: Exciton-phonon coupling in semiconductor nanocrystals

Exciton-phonon coupling (EPC) refers to the dependence of electron-hole state energies on displacement of the nuclei along a phonon coordinate.  The magnitude and frequency distribution of EPC influences the efficiencies of important photophysical processes.  Resonance Raman scattering is an ideal method to probe EPC experimentally, and we are carrying out resonance Raman studies as a function of nanocrystal size, composition, and surface chemistry.  The experimental work is coupled with computational studies that combine fully atomistic calculations of the phonon modes and frequencies with effective mass, particle-in-a-sphere models for the electron and hole wavefunctions and fully quantum mechanical simulations of the resonance Raman intensities.  By measuring and modeling both absolute Raman scattering cross-sections and excitation profiles, we have demonstrated that EPC is fairly constant over a range of CdSe and ZnSe quantum dots of very different sizes, and also is little affected by adding a CdS shell to delocalize the electron wavefunction.  However, ZnSe/CdSe alloyed quantum dots exhibit strongly enhanced EPC which we attribute to localization of the hole wavefunction in locally Cd-rich regions within a random alloy.  














	








Recent publications on this topic

Chen Lin, Ke Gong, David F. Kelley, and Anne Myers Kelley.  Size-dependent exciton-phonon coupling in CdSe nanocrystals through resonance Raman excitation profile analysis.  J. Phys. Chem. C 119, 7491-7498 (2015).

Chen Lin, Ke Gong, David F. Kelley, and Anne Myers Kelley.  Electron-phonon coupling in CdSe/CdS core/shell quantum dots.  ACS Nano 9, 8131-8141 (2015).

Anne Myers Kelley.  Comparison of three empirical force fields for phonon calculations in CdSe quantum dots.  J. Chem. Phys. 144, 214702 (2016). 

Ke Gong, David F. Kelley, and Anne Myers Kelley.   Resonance Raman spectroscopy and electron-phonon coupling in zinc selenide quantum dots.  J. Phys. Chem. C 120, 29533-29539 (2016).

Ke Gong, David F. Kelley, and Anne Myers Kelley.  Non-uniform excitonic charge distribution enhances exciton-phonon coupling in ZnSe/CdSe alloyed quantum dots.  J. Phys. Chem. Letters 8, 626-630 (2017).

Jamie J. Grenland, Chen Lin, Ke Gong, David F. Kelley, and Anne Myers Kelley.  Resonance Raman investigation of the interaction between aromatic dithiocarbamate ligands and CdSe quantum dots.  J. Phys. Chem. C 121, 7056-7061 (2017).

David Morgan, Ke Gong, Anne Myers Kelley, and David F. Kelley.  Biexciton dynamics in alloy quantum dots.  J. Phys. Chem. C 121, 18307-18316 (2017).

Jamie J. Grenland, Cassandra J. A. Maddux, David F. Kelley, and Anne Myers Kelley.  Charge trapping versus exciton delocalization in CdSe quantum dots.  J. Phys. Chem. Lett. 8, 5113-5118 (2017).

Ke Gong, David F. Kelley, and Anne Myers Kelley.  Resonance Raman excitation profiles of CdS in pure CdS and CdSe/CdS core/shell quantum dots: CdS-localized excitons.  J. Chem. Phys. 147, 224702 (2017).

Cassandra J. A. Maddux, David F. Kelley, and Anne Myers Kelley.  Weak exciton-phonon coupling in CdSe nanoplatelets from quantitative resonance Raman intensity analysis.  J. Phys. Chem. C 122, 27100-27106 (2018).

Anne Myers Kelley.  Exciton-optical phonon coupling in II-VI semiconductor nanocrystals.  J. Chem. Phys. 151, 140901 (2019).

Paul Cavanaugh, Ilan Jen-La Plante, Christian Ippen, Ruiqing Ma, David F. Kelley, and Anne Myers Kelley.  Resonance Raman study of shell morphology in InP/ZnSe/ZnS core/shell/shell nanocrystals.  J. Phys. Chem. C, doi.org/10.1021/acs.jpcc.1c02616 (2021).