Project 1: Engineering Electron-Phonon Coupling in
Quantum Dot Solar Cells
(Sponsor: National Science
Foundation)
High-energy photons (with energy
exceeding the bandgap
of a semiconductor)
from the
solar radiation create
hot electrons, which
are at an effective temperature much greater than that of
the lattice. Through
electron-phonon scattering events these hot electrons will
cool until reaching thermal
equilibrium with the lattice. This is the thermalization
loss, a major
limiting factor in photovoltaic solar energy conversion. A
quantum dot solar cell (QDSC) provides an opportunity to
increase the conversion efficiency by reducing the thermalization loss, as shown in the figure.
The electron-phonon coupling factor will be predicted using
first principle calculations and be measured using ultrafast femtosecond
laser spectroscopy. The goal is to develop the criteria for
the design of the optimized solar cells, which feature
reduced electron-phonon coupling and enhanced cell
efficiency.