The influences of substrate temperature on ambipolar organic heterojunction transistors

Organic heterojunction thin-film transistors are fabricated based on copper phthalocyanine (CuPc) and hexadecafluorophtholocyaninatocopper (F₁₆CuPc) as double active layers, which exhibit typical ambipolar conduction. Several substrate temperatures are utilized to tune film morphology, which results in a remarkable change on the electric characteristics of organic transistors. The highest balanced mobility value of 2.91 × 10⁻² cm²/V s for hole and 1.04 × 10⁻² cm²/V s for electron are obtained by depositing F₁₆CuPc at 150 °C and CuPc at 200 °C, respectively, which are comparable to those conventional single-layer devices. This result demonstrates that the growth conditions of organic heterojunctions play a crucial role in ambipolar devices.