Some Like it Hot: Chemistry with Above-Equilibrium Charge Carriers

Speaker:

Kevin M. McPeak

Department of Chemical Engineering, Louisiana State University

Abstract:

Above-equilibrium i.e. “hot” carriers have a host of practical applications, not limited to improving the efficiency of solar cells, driving chemical reactions with sunlight, and detecting light on ultrafast timescales. Thus, re- searchers have made a significant experimental and theoretical effort to improve the efficiency of hot-carrier gen- eration and collection. However, short hot-carrier lifetimes still plague the field resulting in devices with <1% effi- ciency. 

McPeak will discuss two distinct approaches for improving the efficiency of hot-carrier processes, 1). critical-coupling of visible light for in situ H2O2 production and 2). noble-transition alloys for interband driven hot-carrier generation in the near-infrared. Critical coupling of gold nanoparticles to a low-cost aluminum film using a thin ZnO spacer layer provides a greater-than three-fold enhancement in H2O2 generation as compared to uncoupled structures. Furthermore, 5 nm Au50Pd50 films excited at 1550 nm generate 20-fold more 0.8 eV hot holes than pure Au with a three-fold longer lifetime than pure Pd. McPeak will present a fundamental perspective on how critical coupling and noble-transition metal alloying can improve both the dynamics and abundance of hot-carri- ers.