Charge carrier generation in a dye sensitized liquid crystal

The photocarrier generation and recombination mechanism in double layer cells of dye sensitized liquid crystalline hexahexylthiotriphenylene (HHTT) have been studied by steady-state photoconduction measurements. From the dependence of the photocurrent on light intensity we could determine the charge carrier generation mechanism in an azo pigment 4,4’-[(2,5-diphenyl1,3,4-oxadiazol)-bis(azo)]-bis[3-hydroxy-(2H-benzimidazo[2,1-a]benz[d,e]isoquinolin-7-one)] as surface enhanced whereas in titanylphthalocyanine charge generation takes place in the bulk of the dye. We investigated the actionspectra of a single HHTT cell and an azo sensitized cell in the different phases of HHTT to show the influence of azo on the spectral response of the photocurrent. The quantum efficiency in a single HHTT cell as well as in a double layer cell with azo as charge generation layer was determined. By solving the diffusion equation for excitons we carried out an estimation of the exciton diffusion length in azo.