Exciton intrachain

Because of the similarity between the ps spectra of DOO-PPV and P3BT films, it is reasonable to assume that the PM at t=0 ps in the latter films is also mostly due to the photogenerated intrachain excitons. In order to confirm this assump-... 

Using a variety of transient and CW spectroscopies spanning the time domains from ps to ms, we have identified the dominant intrachain photoexcitations in C )-doped PPV films. These are spin-correlated polaron pairs, which are formed within picoseconds following exciton diffusion and subsequent dissociation at photoinduced PPV+/Cw> defect centers. We found that the higher-energy PA band of polaron pairs is blue-shifted by about 0.4 eV compared to that of isolated polarons in PPV. 

In summary, over a large range of interchain distances, the most stable species photogenerated in the lowest excited stale of clusters formed by identical molecules are excitons mostly with an intrachain character. The calculations also show that po-laron-pairs, also referral to as interchain excitons (corresponding to a positive polar-... 

We assume that standard Coulomb-correlated models for luminescent polymers [11] properly described the intrachain electronic structure of m-LPPP. In this case intrachain photoexcitation generate singlet excitons with odd parity wavefunctions (Bu), which are responsible for the spontaneous and stimulated emission. Since the pump energy in our experiments is about 0.5 eV larger than the optical ran... 

The small and weakly time-dependent CPG that persisLs at longer delays can be explained by the slower diffusion of excitons approaching the localization edge [15]. An alternative and intriguing explanation is, however, field-induced on-chain dissociation, a process that does not depend on the local environment but on the nature of the intrachain state. The one-dimensional Wannier exciton model describes the excited state [44]. Dissociation occurs because the electric field reduces the Coulomb barrier, thus enhancing the escape probability. This picture is interesting, but so far we do not have any clear proof of its validity. 

The effect of aggregation or interchain interaction on the triplet excited state in Pt-acetylide polymers was investigated by comparing the optical properties of 1 with the pentiptycene-bridged polymer 15.21 The interchain interaction is prevented by the sterically demanding pentiptycene moiety in 15, and its photophysics is being dominated by the intrachain triplet exciton. 

Dias FB, Maiti M, Hintschich SI, Monkman AP (2005) Intramolecular fluorescence quenching in luminescent copolymers containing fluorenone and fluorene units A direct measurement of intrachain exciton hopping rate. J Chem Phys 122(5) 054904... 

Optical gap the initial excitons are expected to be hot states. Intrachain thermalization may, however, occur within the pump pulse duration. 

PA at 1.48 eV appears instantaneously, shows spectral relaxation to the red, and decays on the same timescale of SE, as shown in Figure 8-9. We assign the observed PA to singlet Bu exciton transitions towards higher lying even parity (Ag) states. We can speculate on the nature of this state within the proposed model. A possible candidate for the final state is the intrachain biexciton. However, its energy level is located below the two-exciton state by an amount equal to the... 

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