THE PHOTOVOLTAIC EFFECT IN ENE-2,3'-BIS(3,2'-DIPHENYL)-QUINOXALINE-7-7'-DIYL)

We have investigated the photovoltaic properties of lene-2,3'-bis(3,2' -diphenyl)-quinoxaline-7-7'diyl) (PPQ) in sandwich structure devices. This polymer contains electron deficient quinoxaline moieties that are expected to give rise to a high electron affinity and to the possibil ity of good electron transport properties. The spectral response of th e photocurrent shows qualitatively that the electron mobility is highe r than the hole mobility in PPQ. The quantum efficiency of the short-c ircuit photocurrent is, however, small, namely only 1.7 X 10(-5)% unde r 10 mW illumination at 420 nm. Doping with tetra(1-dimethylamino-phen yl)-ethynylene (TDPE) increases the quantum efficiency of the short-ci rcuit current to 4 X 10(-4)%, probably due to enhanced exciton dissoci ation. Even with the TDPE dopant, the limiting factor for the photocur rent appears to be charge transport to the contacts. (C) 1998 Publishe d by Elsevier Science B.V.