Tuning of threshold voltage by interfacial carrier doping in organic single crystal ambipolar light-emitting transistors and their bright electroluminescence

Nakanotani, Hajime; Saito, Masatoshi; Nakamura, Hiroaki; Adachi, Chihaya

doi:10.1063/1.3216047

Cited by 67 publications

(79 citation statements)

References 20 publications

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“…More of the light is propagated through the bulk of the crystal in the direction parallel to the gate dielectric rather than in the vertical direction, resulting in strong light emission from the edge of the crystals [3,61,65]. Waveguiding effects have also been used to tune the colour of the emission [69] in single crystal LEFETs.…”

Section: Single Crystal Lefetsmentioning

confidence: 99%

“…In this chapter, devices in which the Ir(ppy) 3 :CBP blend is used as a model phosphorescent emissive layer are described. This study was undertaken to further understand charge injection, charge transport within the devices and recombination in phosphorescent LEFETs.…”

Section: Chaptermentioning

confidence: 99%

“…Since that time, developments have been made to improve the brightness and/or the efficiency of the devices. High mobility polymers [2] or single crystals [3] were used to improve emission characteristics. The device architecture was altered to reflect more of the light out of the device [4].…”

Section: 12mentioning

confidence: 99%

“…The phosphorescent emitter fac-tris-(2-phenylpyridine)iridium (Ir(ppy) 3 ) in a host of 4,4'-bis(N-carbazolyl)-1,1-biphenyl (CBP) has been used as an emissive layer in OLEDs to form green emitting devices [114][115][116]. Blends of Ir(ppy) 3 and CBP have also been used in conjunction with other emissive layers to form white emitting devices [117]. Despite the widespread use of phosphorescent emissive layers in OLEDs, there have only been a limited number of reports in the literature on LEFETs [5,32,[70][71][72].…”

Section: Introductionmentioning

confidence: 99%

“…A co-evaporated layer of the iridium complex Ir(ppy) 3 in a host of CBP was initially used in the devices. Charge injection was studied by using either a Ba or a TPBi/Ba electron-injecting contact.…”

Section: Introductionmentioning

confidence: 99%

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Active channel field-effect transistors: Towards high performance light emitting transistors

Tandy¹

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This thesis describes the study of the development and device physics of organic field-effect transistors and organic light-emitting field-effect transistors. Using chemical and physical properties of organic semiconductors such as light emission, multi-functional devices, or "Active Channel Field-Effect Transistors" can be created. This thesis first describes the creation of basic ambipolar FETs before building on this knowledge to develop ambipolar as well as hole-dominated light emitting field-effect transistors.Ambipolar FETs using a diketopyrrolopyrrole-based copolymer were first investigated in this thesis. When gold electrodes were used, the devices could transport only holes. The charge injection was altered by changing the contacts to aluminium. The devices then were able to conduct both electrons and holes with maximum electron and hole mobilities of order 10 −4 cm 2 V −1 s −1 and 10 −3 cm 2 V −1 s −1 respectively.Light-emitting field-effect transistors were first studied using the model emissive polymerSuper Yellow. Charge injection was studied by altering the electron-injecting contact. Materials used included the low work function metals Ca, Ba and Sm, the inorganic salt Cs 2 CO 3 and the organic material TPBi. Ambipolar devices were created using a neat Super Yellow layer. Electron and hole mobilities in these devices were both of the order of 10 −4 cm 2 V −1 s −1 . The maximum external quantum efficiency was 1.2 ± 0.2 % with a Sm electron-injecting contact, however this occurred at a brightness of less than 1 cd m −2 . A maximum brightness of 43 ± 9 cd m −2 was obtained using a Cs 2 CO 3 -Ag electron-injecting contact in electron accumulation mode. At this brightness, the external quantum efficiency was 0.19 ± 0.04 %.Unipolar devices were also fabricated by adding high mobility charge transport layer of PBTTT underneath the Super Yellow. Since PBTTT had a hole mobility that was orders of magnitude greater than the charge carrier mobilities of Super Yellow, charges were transported in the PBTTT, and recombined within the Super Yellow layer. Super Yellow acted as an emissive layer only. Using this bilayer device architecture, a maximum brightness of 100 ± 4 cd m −2 was obtained with a Ca electron-injecting contact. An external quantum efficiency of 0.04 ± 0.01 % was achieved at the maximum brightness.In order to improve the external quantum efficiency of LEFETs, phosphorescent materials were chosen for use as the emissive layer. A co-evaporated layer of the iridium complex Ir(ppy) 3 in a host of CBP was initially used in the devices. Charge injection was studied by using either a Ba or a TPBi/Ba electron-injecting contact. 4Devices were first fabricated using PBTTT as a hole-dominated charge transport layer.Using a TPBi/Ba electron-injecting contact, the maximum brightness achieved was 200 ± 40 cd m −2with an external quantum efficiency of 0.18 ± 0.01 % at the maximum brightness. Devices were then fabricated using a charge transport layer of DPP-DTT to create ambipolar devices. Electron and ...

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