Controlled growth of ZnPc thin films for photovoltaic applications

The growth of ultra-high-vacuum evaporated ZnPc films was discussed in detail. The effects of growth rate and substrate temperature on the film morphology are investigated by atomic force microscopy. It is clear that growth conditions play a very important role in the surface morphology. High substrate temperature leads to the formation of larger grain. The relationship between ZnPc morphology and organic photovoltaic properties is discussed. PCE of the device using ZnPc grown at 90 °C and 0.12 Å/s is enhanced by a factor of 71% relative to the device using ZnPc grown at 0.02 Å/s. Moreover, the devices prepared at room temperature exhibit relatively higher PCE due to the significant improvements in photocurrent, open-circuit voltage. These results directly imply that controlled growth of the organic films plays a crucial role in further improving the device performances.