Quasi-surface emission in vertical organic light-emitting transistors with network electrode

Keum, Chang‐Min; Lee, Sin Hyung; Lee, Gyu Jeong; Kim, Min Hoi

doi:10.1364/oe.22.014750

Cited by 18 publications

(18 citation statements)

References 28 publications

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“…In this work, we describe the fabrication of an OLED right on top PS-VOFET, a structure known as vertical organic light emitting transistor (VOLET). [26][27][28][29][30] However, similar to other works, the improvement in current densities, using a shorter channel, generates a new challenge: reaching drain saturation regime. Saturation regime is essential for all applications where transistors are used as current sources, in particular, for AMOLED displays where it is important to maintain a fixed current (brightness) even at the expense of higher voltage operation of the pixel's OLED.…”

Section: Introductionmentioning

confidence: 84%

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Reaching saturation in patterned source vertical organic field effect transistors

Greenman

Sheleg

Keum

et al. 2017

Journal of Applied Physics

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Like most of the vertical transistors, the Patterned Source Vertical Organic Field Effect Transistor (PS-VOFET) does not exhibit saturation in the output characteristics. The importance of achieving a good saturation is demonstrated in a vertical organic light emitting transistor; however, this is critical for any application requiring the transistor to act as a current source. Thereafter, a 2D simulation tool was used to explain the physical mechanisms that prevent saturation as well as to suggest ways to overcome them. We found that by isolating the source facet from the drain-source electric field, the PS-VOFET architecture exhibits saturation. The process used for fabricating such saturation-enhancing structure is then described. The new device demonstrated close to an ideal saturation with only 1% change in the drain-source current over a 10 V change in the drain-source voltage. Published by AIP Publishing.

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Section: Introductionmentioning

confidence: 84%

“…Another key advantage of the vertical design is that an organic light emitting diode (OLED) can be fabricated right on top of the transistor, which allow for a large fill factor in active matrix OLED (AMOLED) displays. [26][27][28][29][30][31] The PS-VOFET is formed by stacking several layers (see Fig. 1).…”

Section: Introductionmentioning

confidence: 99%

Reaching saturation in patterned source vertical organic field effect transistors

Greenman

Sheleg

Keum

et al. 2017

Journal of Applied Physics

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“…Only a few fluorescent SG‐OLETs have achieved external quantum efficiency (EQE) over 5% and the peak EQE is only obtained at very low current and luminance . A variation around the SG‐OLET topology is the vertical OLET where hole and electron sources are stacked above the gate whose main objective is to modulate charge injection from one of the sources into the device . This compact topology intimately integrates the actions of switching and light emission, which is particularly suited for display applications.…”

Section: The Literature Benchmark Table Compares Select Olet Work Bamentioning

confidence: 99%

Overlapping‐Gate Organic Light‐Emitting Transistors

Lee

Genoe

et al. 2018

Adv Elect Materials

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The most common OLET architecture relies on a single gate (SG-OLETs) to control the transport of both electrons and holes toward the radiative recombination zone. As a consequence, hole-electron current balance in SG-OLETs can only be achieved at an intermediate gate bias. When driven at high currents, the current imbalance in SG-OLETs usually results in inefficient light emission very close to, or even under the source electrode of the transport layer with the lowest conductivity. [1,[11][12][13][14][15][16] In addition, the emission zone can unpredictably switch from one contact to the other upon small bias changes. [17][18][19][20][21][22] For these reasons, considerable roll-off is observed at increasing bias. Only a few fluorescent SG-OLETs have achieved external quantum efficiency (EQE) over 5% [12,13] and the peak EQE is only obtained at very low current and luminance. [12][13][14]17,[20][21][22] A variation around the SG-OLET topology is the vertical OLET where hole and electron sources are stacked above the gate whose main objective is to modulate charge injection from one of the sources into the device. [23][24][25][26] This compact topology intimately integrates the actions of switching and light emission, which is particularly suited for display applications. But the vertical OLET also suffers from roll-off when driven at high current densities. For all SG-OLET topologies, maintaining the high efficiency at high current level with balanced hole-electron currents remains a major challenge.Dual gate OLETs with two adjacent gates formed by the direct patterning of a single metallic film ("split-gate") have been proposed to decouple electron and hole currents and simultaneously achieve balanced transport at high current density. Unfortunately, the large spatial gap between the gates, more than 1 µm, forms a highly resistive active region which limits the current, resulting in low luminance (below 1000 cd m −2 ) and low EQE (1.3%). [27][28][29][30] Also "opposinggate" dual-gate OLETs have been proposed, where the active organic layer stack is vertically sandwiched between two insulators and two gates that each accumulate one species of charge carriers at either side of the active layer. But the vertical electric field between the gates strongly opposes charge injection and recombination into the central emissive layer, resulting in poor light emission. [31] In this work, we propose a novel dual-gate architecture, the overlapping-gates OLET (OG-OLET), that overcomes the shortcomings of previous OLET topologies. We show how this new device combines the important features of balanced electronhole transport up to high current density and light emission far A light-emitting transistor in which two gates, separated by an insulator, partially overlap in the center of the device is proposed. By accumulating charge carriers in dedicated transport layers, each gate independently controls charge injection into the emissive layer sandwiched between the transport layers. This structure combines the advantages of pinned...

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“…The development of bioelectrodes that are transparent, biocompatible and capable of extended, stable operation in a broad range of biological media is a critical challenge for the field of bioelectronics 1 – 3 . Optoelectronic devices such as light-emitting diodes 4 – 8 , photodiodes 9 – 12 , and phototransistors 13 have been deployed in multiple media, ranging from relatively mild interstitial fluids 14 – 19 to corrosive solutions 20 – 22 . The most important properties for bioelectrodes are high mechanical and chemical stability, high conductivity, high transparency, and excellent biocompatibility.…”

Section: Introductionmentioning

confidence: 99%

Use of SU8 as a stable and biocompatible adhesion layer for gold bioelectrodes

Matarèse

Feyen

Falco

et al. 2018

Sci Rep

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Gold is the most widely used electrode material for bioelectronic applications due to its high electrical conductivity, good chemical stability and proven biocompatibility. However, it adheres only weakly to widely used substrate materials such as glass and silicon oxide, typically requiring the use of a thin layer of chromium between the substrate and the metal to achieve adequate adhesion. Unfortunately, this approach can reduce biocompatibility relative to pure gold films due to the risk of the underlying layer of chromium becoming exposed. Here we report on an alternative adhesion layer for gold and other metals formed from a thin layer of the negative-tone photoresist SU-8, which we find to be significantly less cytotoxic than chromium, being broadly comparable to bare glass in terms of its biocompatibility. Various treatment protocols for SU-8 were investigated, with a view to attaining high transparency and good mechanical and biochemical stability. Thermal annealing to induce partial cross-linking of the SU-8 film prior to gold deposition, with further annealing after deposition to complete cross-linking, was found to yield the best electrode properties. The optimized glass/SU8-Au electrodes were highly transparent, resilient to delamination, stable in biological culture medium, and exhibited similar biocompatibility to glass.

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Quasi-surface emission in vertical organic light-emitting transistors with network electrode

Cited by 18 publications

References 28 publications

Reaching saturation in patterned source vertical organic field effect transistors

Reaching saturation in patterned source vertical organic field effect transistors

Overlapping‐Gate Organic Light‐Emitting Transistors

Use of SU8 as a stable and biocompatible adhesion layer for gold bioelectrodes

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