title: Seeing the invisible plasma with transient phonons in cuprous oxide.
abstract: The emission of phonons from electron-hole plasma is the primary limit on the efficiency of photovoltaic devices operating above the bandgap. In cuprous oxide (Cu2O) there is no luminescence from electron-hole plasma. Therefore, we searched for optical phonons emitted by energetic charge carriers using phonon-to-exciton upconversion transitions. We found 14 meV phonons with a lifetime of 0.916 ± 0.008 ps and 79 meV phonons that are longer lived and overrepresented. It is surprising that the higher energy phonon has a longer lifetime.
authors.affiliation: School of Chemistry, UNSW Sydney, NSW 2052, Australia and Department of Chemistry, Temple University, 1901 N. 13th Street, Philadelphia, PA 19122, USA. pccp@laszlofrazer.com.
authors.forename: Laszlo
authors.identifier: http://orcid.org/0000-0003-3574-8003
authors.initials: L
authors.lastname: Frazer
authors.affiliation: Center for Nanoscale Materials, Argonne National Laboratory, 9700 South Cass Avenue, Building 440, Argonne, IL 60439, USA and Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3112, USA.
authors.forename: Richard D
authors.initials: RD
authors.lastname: Schaller
authors.affiliation: Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3112, USA.
authors.forename: Kelvin B
authors.initials: KB
authors.lastname: Chang
authors.affiliation: Department of Physics, Missouri University of Science and Technology, 117 Physics Building, Rolla, Missouri 65409-0640, USA.
authors.forename: Aleksandr
authors.initials: A
authors.lastname: Chernatynskiy
authors.affiliation: Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3112, USA and Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, USA.
authors.forename: Kenneth R
authors.initials: KR
authors.lastname: Poeppelmeier