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DTSTAMP:20260413T085332
DTSTART:20160331T140000
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URL:https://murmitoyen.com/events/vanille/udem/detail/685056-soutenance-de-
 doctorat-delham-rezasoltani-groupe-silva
LOCATION:Université de Montréal - Pavillon Roger-Gaudry\, 2900\, chemin d
 e la Tour\, Montréal\, QC\, Canada\, H3T 1J6
SUMMARY:Soutenance de doctorat d'Elham Rezasoltani (Groupe Silva)
DESCRIPTION:Excitonic behaviour in polymeric semiconductors
\nDépartement 
 de physique\, Univresité de Montréal
\nGroupe de Carlos Silva
\n 
\nAbs
 tract: 
\nUnderstanding the interrelations between microstructure and ele
 ctronic processes in polymeric semiconductors is of great importance for 
 their use in bulk heterostructures\, as the active part of power-converti
 ng devices such as organic photovoltaic cells or light emitting diodes\, 
 as well as for quantum optoelectronics applications. In this doctoral the
 sis\, two different systems are investigated\; each of these systems repre
 sents a different approach to optimize materials in terms of microstructu
 re and their ability to order on the molecular level. In the first system
 \, by means of quasi-steady-state photoinduced absorption (PIA) and pump-
 modulation-frequency-dependent PIA spectroscopy\, I performed a comprehen
 sive analysis of the working principles of a hybrid photovoltaic cell bas
 ed on nanocrystals of zinc oxide (ZnO) and poly(3-hexylthiophene) (P3HT). 
 The interface surface area between donor (polymer P3HT) and acceptor (ZnO
  nanocrystals)\, where charge generation occurs\, plays a significant rol
 e in the performance of the hybrid photovoltaic cells. To improve the cha
 rge generation mechanism of P3HT:ZnO\, it is therefore essential to modif
 y the P3HT:ZnO interface area. We demonstrated that molecular interface m
 odification with cis-bis(4\,40-dicarboxy-2\,20bipyridine) ruthenium (II) 
 (N3-dye) and a-Sexithiophen-2-yl-phosphonic Acid (6TP) as interface modifi
 ers enhanced the photocurrent and performance in P3HT:ZnO cells. 6TP and 
 N3 attach to the ZnO interface\, thus increasing the donor:acceptor inter
 face area that contributes to enhanced charge separation. Furthermore\, 6
 TP and N3 reduce the ZnO traps that reduces recombination. In the second
  part\, I introduced a processed solid-like ultra-high-molecular-weight p
 olystyrene polymeric host matrix to trap and protect poly [2-methoxy\, 5-(
 2’-ethylhexoxy)-1\,4-phenylene vinylene-PPV] (MEH-PPV) solution for use 
 in quantum optoelectronic devices. Previous work by others has shown that
  MEH-PPV in solution undergoes a Conformation transition from coiled Conf
 ormation at high temperatures (blue-phase) to a chain-extended Conformati
 on at low temperatures (red-phase). The chain-extended Conformation of ME
 H-PPV solution favours the characteristics needed to improve quantum opto
 electronic devices\, however the solution cannot be incorporated into the
  device. We demonstrated that the red-phase feature of MEH-PPV in solution
  maintains in a processed solid-like ultra-high-molecular-weight polystyr
 ene polymeric host matrix (MEH-PPV/UHMWPS gels)\, by means of temperature
 -dependent photoluminescence (PL) spectroscopy (ranged from 290K down to 
 80 K). The red-phase of MEH-PPV/UHMW PS gels manifest itself as narrow li
 newidths and enhanced 0
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