Text Box: Electron-phonon coupling in semiconductor nanocrystals

Electron-phonon coupling refers to the dependence of electronic state energies on displacement of the nuclei along a phonon coordinate.  The magnitude and frequency distribution of electron-phonon coupling contributes to the time scales and efficiencies of several photophysical processes of fundamental and technological significance in semiconductor nanocrystals including carrier multiplication and interfacial charge separation.  Yet little consensus has emerged from many experimental and theoretical studies of electron-phonon coupling in semiconductor nanocrystals.  Resonance Raman scattering is an ideal method to probe electron-phonon coupling experimentally, and in collaboration with David Kelley’s group we have embarked upon 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.  By measuring and modeling both absolute Raman scattering cross-sections and excitation profiles, we have demonstrated that electron-phonon coupling varies quite strongly from one excitonic transition to another (i.e. different electron and/or hole wavefunctions within the same nanocrystal) but has very little dependence on nanocrystal size within the strongly confined regime.


Recent publications in this field

Anne Myers Kelley.  Electron-phonon coupling in CdSe nanocrystals from an atomistic phonon model.  ACS Nano 5, 5254-5262 (2011).

Anne Myers Kelley, Quanqin Dai, Zhong-Jie Jiang, Joshua A. Baker, and David F. Kelley.  Resonance Raman spectra of wurtzite and zincblende CdSe nanocrystals.  Chem. Phys. 422, 272-276 (2013).

Anne Myers Kelley.  Resonance Raman overtone intensities and electron-phonon coupling strengths in semiconductor nanocrystals.  J. Phys. Chem. A 117, 6143-5149 (2013).

Joshua A. Baker, David F. Kelley, and Anne Myers Kelley.  Resonance Raman and photoluminescence excitation profiles and excited-state dynamics in CdSe nanocrystals.  J. Chem. Phys. 139, 024702 (2013).

Jonathan D. Mooney, Jonathan I. Saari, Anne Myers Kelley, Brenna R. Walsh, Michael Krause, and Patanjali Kambhampati.  Control of phonons in semiconductor quantum dots via femtosecond pulse chirp-influenced wavepacket dynamics and polarization.  J. Phys. Chem. B 117, 15651-15658 (2013).

Chen Lin, David F. Kelley, Mikaela Rico, and Anne Myers Kelley.  The “surface optical” phonon in CdSe nanocrystals.  ACS Nano 8, 3928-3838 (2014).

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).