Princeton University

School of Engineering & Applied Science

Singlet exciton fission: Applications to energy harvesting

Dr. Nicholas Thompson, Universal Display Corporation
Equad B205
Thursday, June 25, 2015 - 4:00pm

Abstract: Singlet exciton fission transforms a single molecular excited state into two excited states of half the energy. When used in solar cells it can potentially double the photocurrent from high energy photons, increasing the maximum theoretical power efficiency to greater than 40% for a single junction solar cell.
The steady state singlet fission rate is perturbed under an external magnetic field. I utilize this effect to probe the yield of singlet fission within operating solar cells. Singlet fission approaches unity efficiency in the organic semiconductor pentacene for layers more than 5 nm thick. Using organic solar cells as a model system for extracting photocurrent from singlet fission, I exceed the conventional limit of 1 electron per photon, realizing 1.26 electrons per incident photon.
One proposed device architecture for high power efficiency singlet fission solar cells coats a conventional inorganic semiconducting solar cell with a singlet fission molecule. This design requires energy transfer from the non-emissive triplet exciton to the inorganic semiconducting material, a process which has not been demonstrated. Using colloidal nanocrystals, I demonstrate that the triplet exciton can migrate from tetracene to the nanocrystal with near unity efficiency. This enables future devices where the singlet fission material and nanocrystal system energy transfers triplet excitons to an inorganic solar cell.
Bio: Nicholas Thompson is currently a research scientist at Universal Display Corporation. He received his BS in Materials Science and Engineering from the University of Wisconsin-Madison in 2009 and his Ph.D. in Materials Science and Engineering from the Massachusetts Institute of Technology in 2014 under the direction of Marc Baldo.