Upcoming Colloquia

Carrier Multiplication: Experimental Aspects and Practical Implications

Victor Klimov

Softmatter Nanotechnology and Advanced Spectroscopy,
Chemistry Division
Los Alamos National Laboratory,
Los Alamos, New Mexico 87545, USA

Monday, March 29, 10am

Chemistry Division Auditorium, TA-46, Bld. 535, Rm. 103


The efficient conversion of photon energy into electrical charges is a central goal of much research in physics, chemistry, and biology, especially in areas such as photovoltaics, photocatalysis, and photosynthesis. The usual assumption is that absorption of a single photon by a semiconductor or a molecule produces a single electron-hole pair (exciton), while the photon energy in excess of the energy gap is dissipated as heat by exciting molecular or lattice vibrations (phonons). Under this assumption, the maximum power-conversion efficiency of solar cells is limited to ~31% (the Shockley-Queisser limit). In principle, one can surpass this limit using carrier multiplication, a process in which absorption of a single photon produces not one, but multiple excitons. In this lecture, I will review the current status of carrier multiplication research and describe some of the challenges concerning experimental measurements of multiexciton yields and understanding the mechanisms for multiexciton generation and competing energy relaxation processes. I will also briefly discuss the practical implications of this effect for solar-energy conversion technologies.