Hot Carrier and Phonon Relaxation Dynamics for Photovoltaics

Photovoltaic (PV) energy conversion relies on the formation of carriers’ populations out of equilibrium with their environment under continuous illumination. Conventional PV takes advantage of a non-equilibrium population which translates into a quasi-Fermi level splitting to generate a photo voltage. By contrast, hot carrier solar cells build a out-of-equilibrium temperature which in turn increases to photovoltage and allows in theory to reach power conversion efficiency exceeding the Shockley Queisser limit. To achieve such an imbalance, it is necessary to impede the net energy relaxation of photo-generated carriers, which largely takes place through phonon interactions. Several strategies have been considered and successfully implemented to obtain a hot carrier effect in III-V materials, notably by optimizing the absorber’s architecture [1], by introducing nanostructures [2], by tailoring the acoustic phonon density of states [3] or by relying on intervalley scattering [4].<br/>In this presentation, I will present how hot carriers’ relaxation and transport are modelled using both empirical and theoretical models [5-7]. An emphasis will be set on the optical assessment of hot carriers’ thermodynamic properties using photoluminescence measurements with absolute calibration [6]. This will allow comparison between models and experimental data on a variety of heterostructures.<br/>[1] M. Giteau <i>et al.</i>, <i>J. Appl. Phys.</i>, 2020<br/>[2] D.-T. Nguyen <i>et al.</i>, <i>Nat. Energy</i>, 2018<br/>[3] H. Esmaielpour <i>et al.</i>, <i>Appl. Phys. Lett, </i>2021.<br/>[4] H. Esmaielpour <i>et al.</i>, <i>Nat. Energy</i>, 2020.<br/>[5] A. Le Bris <i>et al</i>, <i>Energy & Environ. Sc.</i>, 2012.<br/>[6] H. Esmaielpour <i>et al.</i>,<i>J. Appl. </i><i>Phys.</i>, 2020.<br/>[7] F. Gibelli <i>et al.</i>, <i>Phys. </i><i>Rev. Appl. </i>, 2016