Photogeneration of charge carriers in segmented arylamino-PPV derivatives

Stationary photoconductivity has been measured for sandwich cells of three arylamino-PPV derivatives between gold and aluminum electrodes. Photoaction spectra recorded under forward bias resemble well the shape of solid state photoexcitation spectra, indicating that the photocurrent is dominated by bulk photogeneration of charge carriers. Even though the photoaction spectra were similar in shape, maximum charge collection efficiencies depended strongly on the choice of the substituents to the PPV-backbone. Under reverse bias the photoaction spectra depend on illumination conditions. The data are interpreted by the build-up of a negative space charge region by immobile photogenerated electrons. We could identify a contribution by photocurrent multiplication, which is caused by the accumulation of photogenerated electrons near the Al/polymer interface. (C) 1999 Elsevier Science B.V. All rights reserved.