Correlation between conjugation length and non-radiative relaxation rate in poly(p-phenylene vinylene): a picosecond photoluminescence study

Theoretical study of the alkoxyls groups effect on PPV-ether excited states, a relationship with femtosecond decay

Based on Density Functional Theory (DFT), the effect of alkoxyl substituents groups on the excited states of new PPV derivative (PPV-ether) are studied. Thus differences on the relaxation energy, the atomic charge distribution and the conjugation length at their excited state are interpreted on the pathways of the nature on the emissive species. Photoluminescence and optical spectra of the corresponding modeling structures are carried out. Furthermore, the life time at the excited state are emphasized either theoretically from oscillator strength or experimentally from time resolved photoluminescence.

Light-Emitting Diodes Based on Conjugated Polymers: Control of Colour and Efficiency

Studies of the effect of different electrode combinations on the device characteristics of simple three layer light-emitting diodes (LEDs) prepared with poly(ρ-phenylenevinylene) (PPV) as the emissive layer sandwiched between two metal contacts have shown that it is generally more difficult to inject electrons than holes. In order to improve the efficiency of such devices it is, therefore, necessary to develop methods to enhance the injection of electrons and we illustrate here one example where we have successfully achieved this by the introduction of a further, electron transport, layer. The result is an eight fold increase in efficiency over our best three layer PPV devices. The efficiency is also dependent on the details of the polymer electronic structure and using a family of copolymers we have been able to produce enhancements in efficiency to values of up to 30 times that of the corresponding PPV devices. Variations in the polymer electronic structure also affect the colour of emission and the same family of copolymers allow control of emission colour from blue/green to orange/red. Supramolecular control of the copolymer electronic structure can be achieved by lithographic patterning and we show that it is possible to produce regions within a single polymer film that possess different π-π* energy gaps.