The photovoltaic effect in poly(p-phenylene-2,3′-bis(3,2′-diphenyl)-quinoxaline-7-7′- diyl)

We have investigated the photovoltaic properties of poly(p-phenylene-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 possibility of good electron transport properties. The spectral response of the photocurrent shows qualitatively that the electron mobility is higher than the hole mobility in PPQ. The quantum efficiency of the short-circuit photocurrent is, however, small, namely only 1.7 × 10-5% under 10 mW illumination at 420 nm. Doping with tetra(1-dimethylamino-phenyl)-ethynylene (TDPE) increases the quantum efficiency of the short-circuit current to 4 × 10-4%, probably due to enhanced exciton dissociation. Even with the TDPE dopant, the limiting factor for the photocurrent appears to be charge transport to the contacts. © 1998 Published by Elsevier Science B.V.