1. The Light Emitting Field Effect transistor (LEFET) as the route to injection lasers fabricated from luminescent semiconducting polymers Alan J. Heeger, University of California-Santa Barbara, DMR 0602280 hv Gate Drain (Ag) Gate Dielectric Source (Ca ) Conjugated Polymer + + + + + + + - - - - - - - - - Structure of the LEFET with a gate-induced p-n junction; the emission zone coincides with the junction region where there are electrons in the conduction band and holes in the valence band. E-beam lithography --- master on Si 1d array of lines --- DFB design for 559 nm Id array (DFB) Imprinted into PVA 1d array (DFB) Imprinted on PVA with Luminescent polymer on top EL spectrum (green) and PL spectrum (black) of the LEFET. Inset shows and optical microscope image of the device. EL emission (see arrow) is close to the edge of the Ca electrode. Molecular structures of PBTTT and Super Yellow. The lower panel is a schematic diagram of the device architecture. Solution processed light emitting field-effect LEFETs with peak brightness exceeding 2500 cd/m 2 have been demonstrated (see data and photo on the right). The results indicate that high brightness LEFETs can be made by using the bi-layer film (hole transporting layer and a light emitting polymer). In the ambipolar regime, there is population inversion in the semiconducting polymer, with a high density of electrons in the  *-band and a high density of holes in the  -band (>10 19 cm -3 in the region near the interface between the semiconductor and the gate dielectric). Thus, the LEFET provides a realistic route toward the fabrication of an injection laser from semiconducting polymers. For completing the injection laser architecture, 1d and 2d resonators have been fabricated by e-beam lithography on Si (left panel on the right). The structures on the Si “masters” can be imprinted into the gate dielectric of the LEFET (e.g. PVA, see middle figure on the right) and incorporated into the LEFET structure (see figure on far right). Plans are directed toward the demonstration of injection lasers fabricated from semiconducting polymers

2. The Light Emitting Field Effect transistor (LEFET) as the route to injection lasers fabricated from luminescent semiconducting polymers Alan J. Heeger, University of California-Santa Barbara, DMR 0602280 Education This is a classic interdisciplinary study involving a combination of physics, chemistry, materials science and device science. The authors include graduate students in the Materials Department (James Swensen and Jonathon Yuen); they collaborated with a post- doctoral researcher whose previous research background is in Physics. The polymer semiconductors are materials from Chemistry. The sophisticated e-beam lithography was carried out by an undergraduate student (Peter Ledochowitsch) in the clean room facility at UCSB. The interdisciplinary nature of the research was a stimulating educational experience for all. Initial results have been published: E. B. Namdas, P. Ledochowitsch, J. D. Yuen, D. Moses, A. J. Heeger, Appl. Phys. Lett. 92, 183304 (2008). The incorporation of the 1d and 2d resonator structures have not yet been described in the literature. Outreach Light emitting diodes, thin film transistors and light emitting field effect transistors fabricated from semiconducting polymers continue to be of interest as components of low-cost and printable plastic electronic circuits. Integration of low-power organic TFTs into OLED arrays leading to all-plastic displays would significantly reduce fabrication costs. The demonstration of high brightness LEFETs and the incorporation of imprinted resonators into the polymer LEFET structure are important miletones toward the fabrication of injection lasers from semiconducting polymers. The successful demonstration of electrically driven injection lasers remains as a major goal of the field. Professor Heeger has given invited (Keynote and Plenary) lectures on the results of this research at conferences in the United States, Europe and Asia.