Surface Plasmon-mediated Luminescence in Organic Field-effect Transistors
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1029-F09-36
Surface Plasmon-mediated Luminescence in Organic Field-effect Transistors Akira Watanabe1, and Hirokazu Tada1,2 1 Materials Physics, Osaka University, 1-3, Machikaneyama, Toyonaka, Japan 2 JST-CREST, Kawaguchi, Japan ABSTRACT We prepared novel type light-emitting organic field-effect transistors (LEOFETs) based on pentacene, in which thin metal wires were inserted between the source and drain electrodes of Au/Cr on SiO2/Si substrates. The luminescence was observed along the inserted metal wires isolated electrically from the drain, source and gate electrodes. The luminescence spectrum was identical to that of pentacene films and its intensity was proportional to the channel current. The light emission was thought to be generated through energy transfer to the pentacene films from plasmon excited on metal surfaces by current injection INTROCUCTION Considerable attention has recently been paid to light-emitting organic filed-effect transistors (LEOFETs) because of their potential applications to novel opto-electronic devices [1-6]. In most LEOFETs, light emission occurs through the recombination of carriers injected from electrodes. Various efforts have been, thus, made to improve injection and transport properties of minority carriers in organic materials [4-6]. On the other hand, light emission was frequently observed when we applied reverse bias voltages, that is, positive bias voltages, to the drain electrode for p-type FETs with grounded source and negatively biased gate electrodes. In this circuit, minority carriers were not injected into organic semiconductors. Nevertheless, the luminous intensity increased with drain voltage. Figure 1(a) shows typical output characteristics of pentacene-based FET at a p-channel accumulation mode. When the drain electrode was biased negatively with respect to the grounded source electrode, the current increased with the gate voltage (biased also negatively) and the saturation in current was observed in most case. In this circuit, holes are injected from the source electrode into organic materials and flow into the drain electrode. Electrons are occasionally injected from the drain electrode at high bias voltage, which generates the light emission along the source electrode through the recombination of carriers. When we use a low work function metals for the drain electrode, electrons are more smoothly injected and intense light emission was detected in the ambipolar operation mode.
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(b)
Figure 1. Output characteristics of a pentacene-based FET: (a) forwarded bias region (Vds
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