Near Infrared Photoresponsive Organic Field-effect Transistor By Utilizing Pentacene/PbPc Heterojunction

Photoresponsive organic field-effect transistor (photOFET) as a new type of photodetector have attractted more and more attention attributed to low cost, easy preparation of large-area film, flexible and other features. At present, most photOFET are fabricated by utilizing single active layer or anisotype heterojunction which consists of two semiconductors with dissimilar type of conductivity. Yet the isotype heteroj unction, which consisted of two semiconductor materials with same type of conductivity, is rarely studied and applied in the field of photOFET. In this dissertation, near infrared photOFET achieved by organic isotype heteroj unction based on pentacene and lead phthalocyanine (PbPc) were fabricated. And we have compared the performances of the isotype heterojunction photOFET (iso-photOFET) and the anisotype heterojunction photOFET (aniso-photOFET) based on C60and PbPc.1. The single-layer photOFET based on pentacene or PbPc were prepared, and the effects of different source/drain electrode materials (Au or Ag) on the device performances were investigated. It was proved that the pentacene has excellent hole-transport ability and PbPc has high near-infrared light absorption coefficiant. The Ohmic contact at the interface between Au electrodes and PbPc or pentacene active layer could effectively increase the field-effect mobility of the single-layer photOFET.2. The photosensitive performances of p-P isotype heteroj unction photOFET with different electrode materials was studied. The results indicated that the photosensitive performance of p-P iso-photOFET was much better than that of PbPc single-layer photOFET, and the photosensitive properties were improved by the schottky contact between silver electrodes and PbPc layer. Additionally, the effects of pentacene layer’s thickness on the photosensitive properties of p-P iso-photOFET were investigated, and the optimized thickness of pentacene transport layer in iso-photOFET was obtained.3. Comparing to the photOFET with C60/PbPc anisotype heterojunction, the p-P iso-photOFET could achieve good field-effect characteristics and superior photosensitive performances as well as better stability.