Bon Won Koo

Conducting Behavior of Carbosilane Dendrimers Including Palladium Ions

The conducting behavior of dendritic carbosilanes including palladium ions (Pd2+) has been measured. The palladium ion containing dendrimers were prepared by the addition of palladium dichloride to double-layered dendritic carbosilanes, which consist of phenylethynyl groups (−C≡CPh) on the outmost periphery as well as phenylethenyl and propyleneoxy groups (−CH=CPh− and (CH2)3O−) in the inner shell. By measuring conductivities, palladium ion containing dendrimers revealed an increasing tendency according to the increasing number of double bonds in the inner shells of dendritic carbosilanes.

10.3: 4.0 Inch Organic Thin Film Transistor (OTFT) Based Active Matrix Organic Light Emitting Diode (AMOLED) Display

We have developed a 4.0 inch pentacene organic thin-film transistors (OTFTs) based active matrix organic light-emitting diode (AMOLED) display. To achieve bright and uniform displays, we have investigated several process issues unique to OTFT-based OLEDs. A bottom contact structure was used to fabricate the pentacene TFT backplane. Fine metal masking (FMM), laser ablation technique (LAT), and polyvinyl alcohol based patterning method were used to isolate the pentacene active layer. The low processing temperature (maximum 150°C) may allow the use of polymeric substrates and lower cost processing. Uniform TFT performance is achieved with reasonably good mobility and on/off ratio. The initial OLED display performance is also presented.

Geometric Effect of Channel on Device Performance in Pentacene Thin-Film Transistor

We fabricated pentacene thin film-transistors on a glass substrate with a SiO2 layer via thermal evaporation in ultrahigh vacuum. We investigated the influence of channel length, channel width, and the deposition rate of a pentacene layer on organic thin film transistors (OTFTs) performance. Field-effect mobility of the transistors markedly increased as channel width decreased and channel length increased. The maximum drain current of OTFTs increased as channel length decreased. These observations indicate that the grain boundary scattering of charge carriers in the pentacene layer is a major hurdle in charge conduction, similarly to the observation in poly-Si TFTs. The maximum field-effect mobility was 0.69 cm2/Vs for a device prepared at 0.1 A/s with a 50 µm channel length and a 20 µm channel width. Channel width/length ratio (W/L) as well as the deposition rate of the pentacene layer should be carefully chosen to increase field-effect mobility and maximum drain current in OTFTs.