ELECTROLUMINESCENCE IN CONJUGATED POLYMERS - EXCITED-STATES IN CYANO-DERIVATIVES OF POLY(P-PHENYLENEVINYLENE)

Processible conjugated polymers can be used to fabricate a range of th in-him diodes which can be designed to show good characteristics both as electroluminescent diodes and as photoconductive diodes. We highlig ht the improvement to the electroluminescence efficiency that can be p roduced by the use of two polymer layers selected so that the heteroju nction between the two layers is able to confine charge and, thus, bri ng about electron-hole capture to generate excitons at this interface. We present results on the photophysical properties of the cyano-subst ituted poly(phenylenevinylene)s which provide electron transport layer s in these heterostructure devices; we find evidence for strong interc hain interactions (excimer formation) for the neutral excited states i n these polymers, with strong red shifts of the luminescence, though p reserving high photoluminescence efficiencies.