CPM Seminar

Metal/organic interface formation in organic thin-film transistors

Ian Hill

Dalhousie

Organic electronics have reached the early stages of commercial viability. Personal electronic devices incorporating small displays based on organic light emitting devices (OLEDs) are now available. Many key challenges still remain, however, which are currently hindering wide-ranging adoption of organic electronic devices. Shortcomings of present day devices include, but are not limited to, poor charge carrier mobilities, high contact resistance at metal/organic interfaces, poor device stability and a lack of inexpensive patterning techniques which do not degrade the electrical properties of the organic films. Due to the amorphous or polycrystalline nature of these materials, and their relatively low process temperatures (< 100C), organic electronics are potentially inexpensive, and can be processed on large-area, flexible substrates, such as PET or PEN plastics. Organic thin-film transistors (OTFTs) exhibit performance similar to their amorphous silicon (a-Si) counterparts, leading many researchers to suggest that OTFTs may replace a-Si as the technology of choice for active-matrix display backplanes. OTFTs can be fabricated on flexible, plastic substrates that may enable continuous roll-to-roll fabrication. Such techniques can be more than an order of magnitude less expensive than traditional batch processing of glass-based a-Si devices. Recent studies have cited evidence of large source/drain contact resistance in OTFTs. This resistance may limit the current-carrying ability of the devices, lead to underestimates of important device parameters, such as the semiconductor mobility, and restrict their utility in active-matrix backplanes, due to the resulting R-C charging time of an individual pixel. The evidence of contact resistance, and its interpretation, will be presented and discussed in the context of metal/organic interface formation. Recent results of physical device simulations will be presented and compared with experimental data.