AVS 45th International Symposium
    Organic Electronic Materials Topical Conference Monday Sessions
       Session OE+EM-MoA

Invited Paper OE+EM-MoA1
Organic Thin Film Transistors

Monday, November 2, 1998, 2:00 pm, Room 327

Session: Organic Thin Film Devices II: Transitors and Transport
Presenter: T.N. Jackson, The Pennsylvania State University
Correspondent: Click to Email
Over the past several years the performance of organic thin-film transistors (OTFTs) has improved dramatically and it now appears likely that they will find application in displays or other low-cost large-area electronic applications. Small molecule materials such as oligothiophenes and oligoacenes have shown the most progress. When deposited by thermal evaporation onto substrates held at elevated temperature these materials often form thin films with strong molecular ordering; such ordering may be important for obtaining large field-effect mobility and other desirable electrical characteristics. In particular, pentacene thin films deposited at a few Å/s onto substrates held at 50 - 100 °C typically have micron-sized grains, and OTFTs using pentacene as the active layer have demonstrated field-effect mobility as large as 1.5 cm@super 2@/V-s, current on/off ratio larger than 10@super 8@, near zero threshold voltage, and subthreshold slope less than 1 V/decade; all these characteristics are similar to those typically observed for a-Si:H thin film transistors (TFTs). Polymeric semiconducting materials are also of interest since they may offer a simple path to solution-processable devices. Thin films of these materials can often be solvent cast which leads to films that are less well-ordered than evaporated small molecule films; however, field-effect mobility near 0.05 cm@super 2@/V-s has been demonstrated for alkyl-substituted soluble polythiophenes. In addition to all-organic applications, OTFTs show promise for integration with a-Si:H TFTs. The field-effect mobility of p-channel OTFTs and n-channel a-Si:H TFTs are similar and integrated organic/a-Si:H devices can provide a simple complementary circuit technology.