Study of the characteristics of organic thin film transistors based on different active layers of pentacene and CuPc thin films

The surface morphology and crystallization of pentacene and CuPc films deposited on SiO2 substrate are characterized by Xray diffraction (XRD) and scaning electron microscopy (SEM). It was observed that the pentacene film has island structure, the sizes of islands were about 100 nm. The pentacene has clearer orientation than CuPc. We also studied organic thin film transistors (OTFTs) with different active layers of pentacene and CuPc, fabricated by shadow mask to investigate the characteristics of the device. The active layers pentacene and CuPc have the thickness of 40 nm, the thickness of gate insulator layer SiO2 is 250 nm and the ratio of width to length (W/L) of device channel is 20. We analyzed the property of devices by Keithley 2410 I-V. The results presented here show that OTFTs devices in which pentacene and CuPc are used as active layer exhibited the field-effect mobility (mu(EF)) of 1.201 cm(2)/V center dot s and 0. 0694 cm(2)/V center dot s, threshold voltage (V-th) of -20 V and -15 V, and (on/off) current radio of 10(4) and 10(5), respectively.