Probing hot-carrier dynamics in photovoltaic devices

The study of hot carrier dynamics in semiconductors, driven out of equilibrium by strong electrical and/or optical fields, is critical to the function of a broad range of microelectronic technologies. While the carriers in such materials typically equilibrate rapidly (on sub-100-fs time scales), efficiently reaching some "hot-carrier" temperature, electron-phonon energy exchange is generally a much slower process (occurring on ns scales) that limits the overall heating of such systems. Understanding the mechanisms of energy transfer via electron-phonon coupling is therefore critical to the quantitative design of advanced electronic/optoelectronic devices. In this presentation I will describe how fast (ns-duration) electrical pulsing of semiconductors can be used to un-derstand the nonequilibrium operation of a variety of electronic devices. These include charge-density-wave materials, in which the roles of field- and thermally-driven processes in resistive switching can be distinguished, 2D van der Waals heterostructures, in which the hot-carrier dynamics is impacted by Moire miniband formation, and novel solar absorbers that use inter-valley transfer for hot-carrier solar cells.