Organic phototransistor based on intramolecular charge transfer in a bifunctional spiro compound

Saragi, Tobat P. I.; Pudzich, Robert; Fuhrmann, Thomas; Salbeck, Josef

doi:10.1063/1.1690110

Cited by 160 publications

(131 citation statements)

References 17 publications

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“…OPTs that have been reported before normally show a response time of more than 10 s since the trapping process of electrons at the semiconductor/insulator interface is relatively slow. 13,20,22 It is worth noting that the OPTs reported in this paper show a much faster response to light illumination due to a different sensing mechanism, which will be explained later. As shown in Fig.…”

Section: Resultsmentioning

confidence: 88%

“…One type is based on the mechanism of trapping excited electrons at the insulator/semiconductor interface of the device under light illumination, which normally induces a positive shift of the threshold voltage of the device. OPTs fabricated by thermal evaporation of some oligomers including pentacene, [13][14][15][16] rubrene, 17 and others [18][19][20] are this type of devices. In addition, solution processible OPTs based on conjugated polymers, such as poly͑9,9-dioctylfluorene-co-bithiophene͒ ͑F8T2͒ ͑Ref.…”

Section: Introductionmentioning

confidence: 99%

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Highly photosensitive thin film transistors based on a composite of poly(3-hexylthiophene) and titania nanoparticles

Yan

Mok

2009

Journal of Applied Physics

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Organic phototransistors based on a composite of P3HT and TiO 2 nanoparticles have been fabricated, which show high photosensitivity, fast response, and stable performance under both visible and ultraviolet light illumination, and thus they are promising for applications as low cost photosensors. The transfer characteristic of each device exhibits a parallel shift to a positive gate voltage under light illumination, and the channel current increases up to three orders of magnitude in the subthreshold region. The shift in the threshold voltage of the device has a nonlinear relationship with light intensity, which can be attributed to the accumulation of electrons in the embedded TiO 2 nanoparticles. It has been found that the device is extremely sensitive to weak light due to an integration effect. The relationship between the threshold voltage change and the intensity of light illumination can be fitted with a power law. An analytical model has been developed to describe the photosensitive behavior of the devices. It is expected that such organic phototransistors can be developed for sensing different wavelengths based on different semiconducting polymers and semiconducting nanoparticles.

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Section: Resultsmentioning

confidence: 88%

Section: Introductionmentioning

confidence: 99%

Highly photosensitive thin film transistors based on a composite of poly(3-hexylthiophene) and titania nanoparticles

Yan

Mok

2009

Journal of Applied Physics

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“…4 Organic phototransistors ͑OPTs͒ are considered to be one of the feasible application of organic thin film transistor ͑OTFT͒ because of their large adsorption properties in ultraviolet ͑UV͒ and visible light and the excellent photocurrent generation efficiency of organic semiconductors. [5][6][7][8][9][10][11][12][13][14][15] More importantly, some OPTs can be fabricated by solution process, [13][14][15] such as printing or spin coating, at room temperature and therefore can be easily integrated in smart clothes, packages, and biological systems as light sensors, biosensors, and multifunctional sensors.…”

mentioning

confidence: 99%

“…OPTs fabricated by thermal evaporation of some oligomers including pentacene, [5][6][7][8] 2,5-bis-biphenyl-4-yl-thieno͓3,2-b͔thiophene, 9 rubrene, 10 N-͓7-͑N , N-diphenylamino͒-9,9Ј-spirobifluoren-2-yl͔-NЈ-͑2,5-di-tert-butylphenyl͒-3,4:9,10-perylenetetracarboxylicdiimide, 11 and 2,7-bis-͑N , NЈ-diphenylamino͒-2Ј,7-bis͑biphenyl-4-yl͒-9,9Ј-spirobifluorene, 12 have been found to be very photosensitive. Normally, a positive shift of the threshold voltage of a OPT can be observed under illumination, which can be attributed to trapping of electrons generated by photons at the insulator/ semiconductor interface of the device.…”

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confidence: 99%

Organic phototransistor based on poly(3-hexylthiophene)/TiO2 nanoparticle composite

Mok

Yan

Chan

2008

Applied Physics Letters

132

101

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Light sensitive phototransistor based on the composite of poly͑3-hexylthiophene͒ and TiO 2 nanoparticles has been developed. The device shows a quick change in channel current under light exposure, which can be attributed to a positive shift of the threshold voltage, while no change in the field effect mobility and off current can be observed. The shift of the threshold voltage is induced by accumulated electrons trapped by the TiO 2 nanoparticles in the channel. The photosensitivity of the device has been found to be dependent on the concentration of TiO 2 nanoparticles, the incident wavelength and the voltage between the source and drain.

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“…Researchers have observed reversible photocurrent and lightinduced threshold voltage shift. [3][4][5] Pentacene-based OTFTs with Ta 2 O 5 gate dielectrics were also proposed to obtain high photoresponsivity. 4 In this paper, an approach to enhance photoresponsivity of pentacene-based OTFTs is proposed.…”

mentioning

confidence: 99%

High Photoresponsivity of Pentacene-Based Organic Thin-Film Transistors with UV-Treated PMMA Dielectrics

Zan

Yen

2008

Electrochem. Solid-State Lett.

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A simple UV-treatment process for poly͑methyl methacrylate͒ ͑PMMA͒ dielectric is proposed to enhance photoresponsivity of pentacene-based organic thin-film transistors. The UV treatment creates excess negatively charged sites on the PMMA dielectric, which makes the device exhibit a large photoinduced current and prolongs persistent conductance recovery. In order to describe time-dependent photoinduced current, double-time constant equations are proposed. Based on time-constant fittings, slow-varied responses are found to be influenced by the UV treatment. The rapid-varied response is independent of gate bias and UV treatment. A plausible model for spatial carrier distribution is discussed and proposed to describe this observed phenomenon. © 2008 The Electrochemical Society. ͓DOI: 10.1149/1.2936224͔ All rights reserved. Organic thin-film transistors ͑OTFTs͒ have received intense attention due to their low cost, light weight, and low-temperature processing compatible with flexible substrates. The integration of OTFTs with other organic devices such as organic light emitting devices and organic solar cells also opens up the field of flexible optoelectronics.1,2 In this field, OTFTs not only act as field-effect transistors, but their application in phototransistors is also important for light detection and photoswitching. However, only a small number of researchers have published works on organic phototransistors. Researchers have observed reversible photocurrent and lightinduced threshold voltage shift.3-5 Pentacene-based OTFTs with Ta 2 O 5 gate dielectrics were also proposed to obtain high photoresponsivity. 4 In this paper, an approach to enhance photoresponsivity of pentacene-based OTFTs is proposed. By using poly͑methyl methacrylate͒ ͑PMMA͒ as the dielectric and applying UVlight treatment, photoresponsivity of OTFTs can be significantly enhanced. By analyzing the response lifetime, the underlying mechanism is investigated carefully. The proposed approach is simple and compatible with the development of all-organic electronics. ExperimentalFirst, the Ni/Pd bilayer was deposited on a glass substrate as a gate electrode. The PMMA was dissolved with a 95 wt % in anisole and was spun onto the gate electrodes. The following was the curing process. The glass substrate was heated with PMMA dielectric on a hot plate at 90°C for 30 min at atmosphere. The solvent was removed and the PMMA was solidified to serve as a gate dielectric. The thickness of the PMMA dielectric was about 360-370 nm. Then, some samples were exposed to UV light ͑Jelight Company, GLS-144 UV Lamp͒, with a wavelength of 175-285 nm and irradiation of 0.043 mW/cm 2 for 90 s. Both the UV-treated PMMA and the untreated ͑standard͒ PMMA dielectrics were transferred into a vacuum chamber for the deposition of 100 nm thick pentacene film and 100 nm thick gold ͑Au͒ electrodes. The device channel width ͑W͒ and length ͑L͒ were 1000 and 100 m, respectively. The illumination system was a combination of a probing bench ͑Cascade microtech, RHM-06͒ and a halogen lamp...

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Organic phototransistor based on intramolecular charge transfer in a bifunctional spiro compound

Cited by 160 publications

References 17 publications

Highly photosensitive thin film transistors based on a composite of poly(3-hexylthiophene) and titania nanoparticles

Highly photosensitive thin film transistors based on a composite of poly(3-hexylthiophene) and titania nanoparticles

Organic phototransistor based on poly(3-hexylthiophene)/TiO2 nanoparticle composite

High Photoresponsivity of Pentacene-Based Organic Thin-Film Transistors with UV-Treated PMMA Dielectrics

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