| Project/Area Number |
18560299
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Electronic materials/Electric materials
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| Research Institution | Niigata University |
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Principal Investigator |
SHINTO Kazunari Niigata University, Institute of Science and Technology, Associate Professor (80272855)
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| Co-Investigator(Kenkyū-buntansha) |
KANEKO Futao Niigata University, Institute of Science and Technology, Professor (20016695)
KATO Keizo Niigata University, Institute of Science and Technology, Professor (00194811)
OHDAIRA Yasuo Niigata University, Institute of Science and Technology, Associate Professor (10361891)
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| Project Period (FY) |
2006 – 2007
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| Project Status |
Completed (Fiscal Year 2007)
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| Budget Amount *help |
¥3,920,000 (Direct Cost: ¥3,500,000、Indirect Cost: ¥420,000)
Fiscal Year 2007: ¥1,820,000 (Direct Cost: ¥1,400,000、Indirect Cost: ¥420,000)
Fiscal Year 2006: ¥2,100,000 (Direct Cost: ¥2,100,000)
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| Keywords | Organic Field-Effect Transistor / Charge Generation Layer / Vanadium Pentoxide / Copper Phthalocyanine / Mobility / Charge Transfer Complex / V_2O_5 |
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| Research Abstract |
In this study, organic field-effect transistors(OFETs)with vanadium pentoxide (V_2O_5)layer were fabricated, and OFET characteristics and operating mechanism were investigated. It is known that V_2O_5 is one of Lewis-acid material and acts as a charge-generation layer in organic light-emitting diodes(OLED5). In such OLEDs, conventional light-emitting units are stacked with V_2O_5 layers in between. Holes and electrons are generated in V_2O_5 layer by applying electric field and are injected into adjacent emissive organic units. It results in improvement of current efficiency in the OLED. However, the V_2O_5 layer has not been applied to other organic devices, such as OFET. We attempted to improve OFET performance by insertion of V_2O_5 layer in OFET. It was considered that carriers could be injected from V_2O_5 layer to organic film by applying voltage. It is expected that the insertion of V_2O_5 layer is easy and useful way to control OFET characteristics.
Copper phthalocyanine was use
… More
d as organic semiconductor. Usual OFETs with CuPc operates for negative gate voltage, because CuPc is p-type material and channels are formed by hole accumulation due to the gate voltage. At first, the characteristics of OFETs with Si/ SiO_2/ CuPc/ V_2O_5 structure were compared to CuPc FET without V_2O_5 layer. Large on-currents were observed by the insertion of V_2O_5 layers. The OFET operated for negative gate voltage, as usual CuPc FET. Then, OFETs with different layer order, that is, Si/ SiO_2 / V_2O_5/ CuPc structure were fabricated. Quite large drain currents were observed for the OFETs with V_2O_5 layer and the OFET operated for inverse polarity of the gate voltage (positive gate voltage). The apparent mobilities were also improved in the above OFETs with V_2O_5 layers. OFET with only V_2O_5 layer for active layer was also fabricated, and the device did not work. It suggested that the channels were not formed in V_2O_5 layers. In order to investigate the operation mechanism, UV-vis absorption spectra and ionization potentials were investigated for the CuPc, V_2O_5 and CuPc film doped with V_2O_5. Each characteristic of CuPc layer was changed due to the doping of V_2O_5. It was considered that CT complex were formed by the interaction between V_2O_5 and CuPc molecules. Hole and electron pairs can be created by separation of the CT complex by gate voltage, and holes can be injected to CuPc layers and contribute to the channel formation. It was also estimated that the injection of holes into the CuPc layer should depend on the electric field direction so that the appropriate gate voltage polarity changed with the film deposition order. The thickness dependences were also investigated and the results suggested that the CuPc and V_2O_5 could interact even at several tens of nano-meters. OFETs with other organic materials and V_2O_5 layer were also fabricated and performance improvement was observed for magnesium phthalocyanine FETs.
It is considered that V_2O_5 insertion can improve performances of various OFETs quite easily by deposition order or thickness control. Furthermore, this method should be useful for constructing electronic devices using OFETs. Less
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