Bulletin of the American Physical Society
APS March Meeting 2018
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session L20: Solar/Energy Conversion: Theory and Devices
11:15 AM–1:39 PM,
Wednesday, March 7, 2018
LACC Room: 308B
Sponsoring Units: GERA FIAP DPOLY
Chair: Ernesto Marinero, Purdue University
Abstract: L20.00003 : Seeing the Invisible Plasma with Transient Phonons in Cuprous Oxide: Deducing Phonon Dynamics using the Phonon-to-Exciton Induced Absorption Triggered by Electron-Hole Plasma Relaxation in Cuprous Oxide*
11:39 AM–11:51 AM
In cuprous oxide (Cu2O) there is no luminescence from electron-hole plasma. The emission of phonons from electron-hole plasma is the primary limit on the efficiency of photovoltaic devices operating above the bandgap. 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.
Cuprous oxide is a semiconductor with a high theoretical photovoltaic/photocatalytic efficiency, composed of abundant and nontoxic elements. Charge carrier/phonon inelastic scattering can be examined by measuring carriers or by measuring phonons. However, in cuprous oxide, both the 3d-like valence and the 4s-like conduction band have positive parity. Therefore electron-hole plasma luminescence is forbidden and not observed. This led us to develop a bulk, femtosecond scale phonon measurement approach.
*NSF DGE-0801685 DMR-1307698 DMR-1121262 DOE DE-AC02-06CH11357 DE-AC36-08GO28308.
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