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SUMMARY:Quantum Dot Growth Technology by MBE for Advanced Photovoltaics - 
 Professor Yoshitaka Okada
DTSTART:20151123T140000Z
DTEND:20151123T170000Z
UID:TALK62526@talks.cam.ac.uk
CONTACT:Teri Bartlett
DESCRIPTION:The talk is one of the seven talks scheduled for the "Universi
 ty of Cambridge – The University of Tokyo Joint Workshop on Quantum Nano
 structures"\, at 14:00-17:00.\nSignificant effort and a rapid progress hav
 e been made today in modeling the device physics as well as practical demo
 nstration of quantum dot intermediate band solar cells (QD-IBSCs).\nPresen
 tly\, demonstration of QD-IBSCs is undergoing various development stages. 
 The first challenge is to establish methods to fabricate high-density QDs 
 arrays or superlattice of low defect density and long carrier lifetimes. T
 he strain-compensated or strain-balanced growth technique by MBE can signi
 ficantly improve the QDs quality and characteristics of solar cells even a
 fter stacking of > QD 100 layers in self-organized heteroepitaxy.\nThe sec
 ond effort is to increase the carrier lifetimes in IB states by controllin
 g the recombination rates such as by using (1) a type-II QD heterostructur
 e that allows a fast spatial separation of electrons and holes\, (2) a hig
 h potential barrier preventing the thermal electron escape out of QDs\, an
 d (3) an electric field damping layer suppressing the field-assisted escap
 e of electrons out of QDs.\nThe last challenge is to realize partially fil
 led IB states in order to maximize photocurrent generation by two-step IR 
 photon absorption. For this\, doping of QDs and photofilling of QDs by lig
 ht concentration as well as photon confinement thin-film structure are all
  considered important.\n
LOCATION:Mott Seminar Room (Mott Building Room 531)\, Cavendish Laboratory
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