Temperature dependent performance of lead phthalocyanine phototransistors

Abstract

Abstract In order to heighten their near infrared light-sensitive characteristics, lead phthalocyanine (PbPc) phototransistors were prepared by vacuum evaporation at various substrate temperatures (T s) of 60°C, 100°C, 140°C and 180°C. The crystalline texture, absorption spectrum and surface morphology of PbPc films were measured. The light-sensitive characteristic measurement results indicated that the photoresponsivity (R) and specific detectivity (D *) of the devices first rise and dwindle as T s grows and a best performance is gained at T s = 100°C. Research on the correlation between substrate-temperature-dependent film properties and device performance showed that the crystal texture, interconnection of grains, light absorption and carrier mobility of PbPc films could be varied by substrate heating, and thereby causing the variations in the device performance for R and D *. Moreover, a model semi-quantitatively describing the variation of photocurrent with optical absorption coefficient and carrier mobility was set up, and some numerical calculations were made base on the model presented.