Intra-molecular properties of DMeOPPV studied by quantum molecular dynamics

Abstract

Introducing methoxy electron donor groups into a poly(para-phenylene vinylene) (PPV) chain will lead to the appearance of unique electronic properties at the molecular scale which should affect the overall properties of light-emitting diodes based on these polymers.Self-consistent quantum molecular dynamics calculations have been used to provide information on intra-molecular properties of poly(2,5-dimethoxy-para-phenylene vinylene) (DMeOPPV), which are relevant for the modelling and characterization of polymer lightemitting diodes at nanometric length scale. We focus our attention in those properties that have been somewhat neglected in previous literature: the charge distribution associated with positive and negative charge carriers and their intra-molecular mobility when an electric field is applied.

Modelling the effect of nonplanarity on charge transport along conjugated polymer chains

“…Walker et al [1] review the main results obtained using continuum macroscopic models. Recently, we made the first attempts to simulate the charge transport along fully conjugated polymer chains of poly(p-phenylene vinylene) (PPV) and some of its derivatives, using a quantum molecular dynamics method [2][3][4]. The comparison between results obtained by this method and the experimental ones permits one to conclude that generally the self-consistent quantum molecular dynamics approach yields reliable predictions of intra-molecular charge mobility.…”

Theoretical study of electric field-dependent polaron-type mobility in conjugated polymers

“…Since conduction in conjugated polymers is believed to be mediated by charge-induced defects (localized charge dressed by lattice distortion) arising from the strong electron-lattice coupling, we use a selfconsistent quantum molecular dynamics method to calculate quantitatively the mobility of these charged defects, known as polarons, on isolated chains of PPV [5], cyano-PPV (CN-PPV) [6] and dimetoxy-PPV (DMeO-PPV) [7] and the dependence of their mobility on the electric field. The effects of conjugation length and conjugation break on the mobility of positive and negative charged polarons on PPV are also discussed.…”

Modelling the effects of molecular arrangements in polymer light-emitting diodes

“…It is also necessary to determine the most energetically favourable position of the injected charge over the chain and its dependence on the strength of the electric field along the chain. In previous work already published [11,[17][18][19] we show that in PPV, cyano-PPV and dimethoxy-PPV the charging of a chain results in a chargeinduced defect in the chain backbone (charge dressed with lattice distortion), which is localized at the centre of the chain if the electric field applied along it is lower than the field needed for intra-molecular charge mobility; otherwise, the injected charge moves toward the chain-end favoured by the electric field. The results of such atomic scale calculations concerning the ionization potential and electron affinity of chains with different numbers of monomer units and the electric field threshold for electron and hole mobility along the chains are summarized in figure 2 and table 1.…”