Light emission from an ambipolar semiconducting polymer field-effect transistor

The successful demonstration of light emitting field-effect transistors (LEFETs) has been worked towards for years within the organic electronics community. The belief was held that if an ambipolar FET could be developed with high enough density of both electrons and holes within the channel region of an FET simultaneously, then recombination of those carriers would result in electroluminescence. The challenge to demonstrating such a device centered on the issue of electron transport; why was electron transport not observed for nearly all SCPs in a field-effect transistor?; Use of a low dielectric constant material to passivate inorganic dielectrics in order to observe electron transport for semiconducting conjugated polymers in a field-effect transistor was verified. A different material, polypropylene-co-1-butene, was shown to passivate various inorganic insulators to eliminate or reduce trap states such that electron transport can be observed for SCPs.; Another challenge to demonstrating an LEFET involved developing a method to deposit a low work function metal as either the source or the drain electrode in the FET structure. In this research, a process was developed in which an SCP FET can be fabricated inside of a nitrogen glove box where one electrode is a high work function metal and the other electrode is a low work function metal with the precision of photolithography using a silicon shadow mask and an angled evaporation technique. As a result, the SCP LED electrodes architecture was successfully transferred to an FET platform as the source and drain electrodes, which we "call two-color electrodes."; In summary, by combining the passivation layer technology which allows for electron transport and the silicon shadow mask/angled evaporation technique which gives two color electrodes, ambipolar SCP LEFETs were demonstrated. Transport data show ambipolar behavior. Recombination of electrons and holes result in a narrow zone of light emission within the channel. The location of the emission zone is controlled by the gate bias. The width of the emission zone is resolved with high resolution using confocal microscopy and found to be 2 mum wide.