What Determines Inhomogeneous Broadening of Electronic Transitions in Conjugated Polymers?

Title data

Hoffmann, Sebastian T. ; Bässler, Heinz ; Köhler, Anna:
What Determines Inhomogeneous Broadening of Electronic Transitions in Conjugated Polymers?
In: The Journal of Physical Chemistry B. Vol. 114 (2010) Issue 51 . - pp. 17037-17048.
ISSN 1520-5207
DOI: https://doi.org/10.1021/jp107357y

Official URL:

Abstract in another language

Energetic disorder is manifested in the inhomogeneous broadening of optical transitions in π-conjugated organic materials, and it is a key parameter that controls the dynamics of charge and energy transfer in this promising class of amorphous semiconductors. In an endeavor to understand which processes cause the inhomogeneous broadening of singlet and triplet excitations in π-conjugated polymers we analyze continuous wave absorption and photoluminescence spectra within a broad range of temperatures for (i) oligomers of the phenylenevinylene family (OPVs) and MEH-PPV in solution and (ii) bulk films of MEH-PPV and members of the poly(p-phenylene) family (PPPs). We use a Franck−Condon deconvolution technique to determine the temperature dependent S1−S0 0−0 and T1−S0 0−0 transition energies and their related variances. For planar compounds, the transition energies can be related to the oligomer length, which allows us to infer the effective conjugation length for the nonplanar compounds as a function of temperature. With this information we can distinguish between intrachain contributions to the inhomogeneous line broadening that are due to thermally induced torsional displacements of the chain elements, and other contributions that are assigned largely to dielectric interactions between the chain and its environment. We find that in solution, temperature-induced torsional displacements dominate the line broadening for the alkyl derivatives of OPVs while in the alkoxy derivatives the Van der Waals contribution prevails. In films, σ is virtually temperature independent because disorder is frozen in. We also establish a criterion regarding the ratio of inhomogeneous line broadening in singlet and triplet states. The results will be compared to a recent theory by Barford and Trembath.

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 > Chair Experimental Physics II - Optoelectronics of Soft Matter > Chair Experimental Physics II - Optoelectronics of Soft Matter - 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 > Chair Experimental Physics II - Optoelectronics of Soft Matter
Result of work at the UBT:	Yes
DDC Subjects:	500 Science > 530 Physics
Date Deposited:	13 Feb 2015 12:44
Last Modified:	13 Feb 2015 12:44
URI:	https://eref.uni-bayreuth.de/id/eprint/6752