Event
Ph.D. Dissertation Defense: Yangyi Yao
Tuesday, April 30, 2019
3:30 p.m.-5:30 p.m.
AVW 2460
Maria Hoo
301 405 3681
mch@umd.edu
ANNOUNCEMENT: Ph.D. Dissertation Defense
NAME: Yangyi Yao
Advisory Committee:
Professor Mario Dagenais, Chair/Advisor
Professor Edo Waks
Professor Edo Waks
Professor Martin Peckerar
Professor Kevin Daniels
Professor Marina Leite
Professor Lourdes Salamanca-Riba, Dean's representative
Date/Time: Tuesday, April 30th, 3:30 - 5:30pm.
Place: AVW 2460
Title: Fabrication and Characterization of Perovskite and Intermediate Band InAs/GaAs Quantum Dot Solar Cells
Abstract:
The concept of intermediate band solar cell was proposed by Luque and Marti in 1990 and has been extensively studied for decades. Previously we have reported high optical saturation intensity of the quantum dot resonance at room temperature for a self-ensemble of un-doped quantum dots (QDs). Operating at cryogenic temperatures leads to a reduction of the saturation intensity. We acquired a liquid-helium cryo-cooler system to support the on-resonance measurement of the quantum dot solar cell (QDSC) at cryogenic temperatures. We measured the photoluminescence of the QDSC to extract the QD energy from 293K to 8K. We modified the on-resonance z-scan set-up with the cryo-cooler to evaluate the saturation effects of the QDs. We studied the photocurrent response and extracted the saturation intensity of the QD ground state from 293K to 170K. We observed a substantial decrease of the saturation intensity as the temperature is decreased, but this intensity is still much higher than one-sun intensity. The intermediate band two photon absorption contribution to the photocurrent enhancement is extremely small even at 170K. By cooling all the way down to liquid helium temperatures, it should be possible to further reduce the saturation intensity.
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