PHOTOCARRIER GENERATION PROCESSES OF PHTHALOCYANINES STUDIED BY PHOTOCURRENT AND ELECTROABSORPTION MEASUREMENTS

We have studied the photocarrier generation processes of copper, oxoti tanium, and tau-metal-free phthalocyanines (Pcs) by measuring the temp erature dependence of transient photocurrent, lifetime of precursor of free carrier, and electroabsorption spectra. No distinct correlation was observed between the photocurrent activation energy and the charge generation efficiency. The lifetimes of some Pcs with different charg e generation efficiencies had little difference. In phase II and Y-for m oxotitanium Pc (TiOPc), electroabsorption signals assignable to CT e xciton bands could be observed, while in amorphous TiOPc only the Fren kel exciton band was observed. The phase II and Y-form TiOPc showed mu ch higher photoconductivities than the amorphous one. These results in dicated that the nature of the excited states, namely the strength of the CT interaction, should dominate the free carrier generation effici ency in the photocarrier generation processes of Pcs.