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The red-phase of poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) : A disordered HJ-aggregate

Title data

Yamagata, Hajime ; Hestand, Nicholas J. ; Spano, Frank C. ; Köhler, Anna ; Scharsich, Christina ; Hoffmann, Sebastian T. ; Bässler, Heinz:
The red-phase of poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) : A disordered HJ-aggregate.
In: The Journal of Chemical Physics. Vol. 139 (2013) .
ISSN 0021-9606
DOI: https://doi.org/10.1063/1.4819906

Official URL: Volltext

Abstract in another language

The ratio of the 0-0 to 0-1 peak intensities in the photoluminescence (PL) spectrum of red-phase poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene], better known as MEH-PPV, is significantly enhanced relative to the disordered blue-phase and is practically temperature independent in the range from T = 5 K to 180 K. The PL lifetime is similarly temperature independent. The measured trends are accounted for by modeling red-phase MEH-PPV as disordered π-stacks of elongated chains. Using the HJ-aggregate Hamiltonian expanded to include site disorder amongst electrons and holes, the absorption and PL spectra of cofacial MEH-PPV dimers are calculated. The PL 0-0/0-1 line strength ratio directly responds to the competition between intrachain interactions which promote J-aggregate-like behavior (enhanced PL ratio) and interchain interactions which promote H-aggregate-like behavior (attenuated PL ratio). In MEH-PPV aggregates, J-like behavior is favored by a relatively large intrachain exciton bandwidth – roughly an order of magnitude greater than the interchain bandwidth – and the presence of disorder. The latter is essential for allowing 0-0 emission at low temperatures, which is otherwise symmetry forbidden. For Gaussian disorder distributions consistent with the measured (inhomogeneous) line widths of the vibronic peaks in the absorption spectrum, calculations show that the 0-0 peak maintains its dominance over the 0-1 peak, with the PL ratio and radiative lifetime practically independent of temperature, in excellent agreement with experiment. Interestingly, interchain interactions lead only to about a 30% drop in the PL ratio, suggesting that the MEH-PPV π-stacks – and strongly disordered HJ-aggregates in general – can masquerade as single (elongated) chains. Our results may have important applications to other emissive conjugated polymers such as the β-p

Further data

Item Type: Article in a journal
Refereed: Yes
Institutions of the University: Faculties > Faculty of Mathematics, Physics und Computer Science > Department of Physics > Lehrstuhl Experimentalphysik II - Optoelektronik weicher Materie > Lehrstuhl Experimentalphysik II - Optoelektronik weicher Materie - Univ.-Prof. Dr. Anna Köhler
Faculties
Faculties > Faculty of Mathematics, Physics und Computer Science
Faculties > Faculty of Mathematics, Physics und Computer Science > Department of Physics
Faculties > Faculty of Mathematics, Physics und Computer Science > Department of Physics > Lehrstuhl Experimentalphysik II - Optoelektronik weicher Materie
Result of work at the UBT: Yes
DDC Subjects: 500 Science > 530 Physics
Date Deposited: 10 Feb 2015 08:09
Last Modified: 09 Mar 2016 08:08
URI: https://eref.uni-bayreuth.de/id/eprint/6657