Photoinduced injection of positive charge carriers

Aromatic molecules in a nonpolar liquid can be excited by light absorption to singulet states which convert to triplet states with lifetimes, in the millisecond time scale. A fraction of these excited molecules will diffuse to the anode and convert to a positive ion by electron transfer. These ions are then injected into the liquid volume and measurements of the drift time, td. can be performed. In solutions of rubrene in benzene (3 to 5 x 10 M), rubrene molecules were excited by a short flash of visible light. Since td,a layer of ions started at the anode giving rise to a constant 

Photoinduced injection of positive charge carriers has not yet been observed in pure saturated hydrocarbons. Studies on the fluorescence of liquid alkanes have established low quantum yields for the process (Rothman et al., 1973) and lifetimes in the nanosecond time scale (Ludwig, 1971). 

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