p- and n-Type Charge Transport in Field-Effect Transistors of Pristine Poly(p-Phenylenevinylene)
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0965-S06-11
p- and n-Type Charge Transport in Field-Effect Transistors of Pristine Poly(pPhenylenevinylene) Hiroshi Kayashima1, Takeshi Yasuda1,2, Katsuhiko Fujita1,2, and Tetsuo Tsutsui1,2 1 Department of Applied Science for Electronics and Materials, Graduate School of Engineering Sciences, Kyushu University, 6-1 Kasuga-koen, Kasuga, Fukuoka, 816-8580, Japan 2 Institute for Materials Chemistry and Engineering, Kyushu University, 6-1 Kasuga-koen, Kasuga, Fukuoka, 816-8580, Japan
ABSTRACT Poly(p-phenylenevinylene) (PPV) thin films were prepared by using drop casting under high gravity condition in a centrifuge and PPV based field effect transistors (FET) were fabricated. PPV FETs with gold source-drain electrodes showed the p-channel characteristics. The field-effect hole mobility was improved to 8.8x10-4cm2V-1s-1 by thermal treatment. PPV FET with calcium source-drain electrodes showed the n-channel characteristics and the field-effect electron mobility was 1.0x10-6cm2V-1s-1. INTRODUCTION Since electroluminescence in poly(p-phenylenevinylene) (PPV) thin films was found in 1990, PPV and its derivatives have been used as electroluminescent materials for organic light emitting diodes (OLED)[1]. The side chains have been chosen and attached to these polymers to solubilize in conventional organic solvents. Wide varieties of PPV derivatives with various side chains have been synthesized. Concentrating organic field-effect transistor (OFET), thiophenecontaining polymers such as poly(3-hexylthiophene) are regarded as a benchmark among πconjugated polymers [2]. The field-effect hole mobility of 10-1 cm2V-1s-1 have been achieved in highly regioregular head-to-tail P3HT. Therefore, little attention have been paid to PPV derivatives as active materials of OFET. The typical PPV derivatives, poly(2-methoxy-5-(2ethylhexyloxy)-1,4-phenylenevinylene), for example, showed relatively low field-effect mobility of 10-4 cm2V-1s-1 [3]. Recently, high field effect hole mobilities of 10-2 cm2V-1s-1 and 10-1 cm2V-1s-1 were demonstrated in a PPV derivative with symmetrical side chains [4] and a phenylenevinylene oligomer [5], respectively. These reports suggested a possibility of high performance FETs by using phenylenevinylene derivatives which can form crystalline or well-developed intermolecular π-π stacking. PPV without side chains would be a good example. Over the past few decades, a considerable number of studies have been conducted on PPV prepared via precursors. There are a lot of reports about the electronic properties. PPV is one of high-resistive semiconductors with the conductivity below 10-12 Scm-1 [6]. However, PPV can turns to a metallic conductor by heavy doping of donors or accepters. High conductivity up to 104 Scm-1 has been reported in H2SO4-doped highly oriented PPV films and highly anisotropic conductivity up to 102 has been demonstrated [7]. Furthermore, the bipolar carrier transport of pristine PPV was investigated by using time-of-flight technique. The hole mobility and electron
mobilities from time-of-flight mea
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