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Theory of excited-state absorption in phenylene-based pi-conjugated polymers

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Title Theory of excited-state absorption in phenylene-based pi-conjugated polymers
 
Creator SHUKLA, A
GHOSH, H
MAZUMDAR, S
 
Subject even-parity states
poly(p-phenylene vinylene)
2-photon fluorescence
transient-absorption
electronic-structure
optical-properties
infinite polyenes
spectroscopy
oligomers
spectra
 
Description Within a rigid-band correlated electron model for oligomers of poly-(paraphenylene) (PPP) and poly-(paraphenylenevinylene) (PPV), we show that there exist two fundamentally different classes of two-photon A(g) states in these systems to which photoinduced absorption (PA) can occur. At relatively lower energies there occur A(g) states which are superpositions of one electron-one hole (1e-1h) and two electron-two hole (2e-2h) excitations, that are both comprised of the highest delocalized valence-band and the lowest delocalized conduction-band states only. The dominant PA is to one specific member of this class of states (the mA(g)). In addition to the above class of A(g) states, PA can also occur to a higher energy kA(g) state whose 2e-2h component is different and has significant contributions from excitations involving both delocalized and localized bands. Our calculated scaled energies of the mA(g) and the kA(g) agree reasonably well to the experimentally observed low- and high-energy PA's in PPV. The calculated relative intensities of the two PA's are also in qualitative agreement with experiment. In the case of ladder-type PPP and its oligomers, we predict from our theoretical work an intense PA at an energy considerably lower than the region where PA's have been observed currently. Based on earlier work that showed that efficient charge-carrier generation occurs upon excitation to odd-parity states that involve both delocalized and localized bands, we speculate that it is the characteristic electronic nature of the kA(g) that leads to charge generation subsequent to excitation to this state, as found experimentally.
 
Publisher AMERICAN PHYSICAL SOC
 
Date 2011-07-17T22:02:57Z
2011-12-26T12:50:31Z
2011-12-27T05:35:40Z
2011-07-17T22:02:57Z
2011-12-26T12:50:31Z
2011-12-27T05:35:40Z
2003
 
Type Article
 
Identifier PHYSICAL REVIEW B, 67(24), -
1098-0121
http://dx.doi.org/10.1103/PhysRevB.67.245203
http://dspace.library.iitb.ac.in/xmlui/handle/10054/4850
http://hdl.handle.net/10054/4850
 
Language en