Photoconduction in Langmuir-Blodgett films of octasubstituted metal-free phthalocyanine molecules

In-plane steady-state photoconduction in Langmuir-Blodgett (LB) films of octasubstituted metal-free phthalocyanine molecules have been studied over a temperature range between 78 and 293K. Deep-level traps localised at grain boundaries of multicrystalline films are believed to be responsible for both dark conduction and photoconduction. Slow and fast relaxation mechanisms are identified from measurements of transient currents. Small changes of substituting chains in the molecule are found to have significant influences on rate and quantum yield of photogeneration of charge carriers in LB films.