Orange‐Red‐Light‐Emitting Field‐Effect Transistors Based on Phosphorescent Pt(II) Complexes with Area Emission

Wawrzinek, Robert; Muhieddine, Khalid; Ullah, Mujeeb; Koszo, Peter B.; Shaw, Paul E.; Grosjean, Arnaud; Maasoumi, Fatemeh; Stoltzfus, Dani M.; Clegg, Jack K.; Burn, Paul L.; Namdas, Ebinazar B.; Lo, Shih‐Chun

doi:10.1002/adom.201600460

Cited by 16 publications

(16 citation statements)

References 51 publications

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“…[12,[14][15][16][35][36][37] This limited efficiency roll-off is confirmed in Figure 4b that represents EQE averaged over the whole linear region as a function of current density. [12,[14][15][16][35][36][37] This limited efficiency roll-off is confirmed in Figure 4b that represents EQE averaged over the whole linear region as a function of current density.…”

Section: Wwwadvelectronicmatdesupporting

confidence: 58%

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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Section: Wwwadvelectronicmatdesupporting

confidence: 58%

Overlapping‐Gate Organic Light‐Emitting Transistors

Lee

Genoe

et al. 2018

Adv Elect Materials

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“…Alternative approaches to n ‐type charge transport have been the use of inorganic semiconductors such as CdS, metal oxides ( e.g ., ZnO, ZTO, and AZO) and metal oxynitride (e.g., ZnON) (Table , hybrid LETs). A much higher charge mobility of up to 19 cm 2 V −1 s −1 and a high channel current ON/OFF ratio (>10 6 ) have been achieved.…”

Section: Let Materialsmentioning

confidence: 99%

“…Notably, instead of detrimental aggregate‐caused luminescence quenching in most Ir(III) complexes, many Pt(II) complexes have lately been shown to exhibit unique aggregate‐induced phosphorescence enhancement (either through metal‐metal‐to‐ligand CT, MMLCT, transition, or restriction of rotation in neat films), representing the high prospect of square‐planar Pt(II) complexes. While neat films of Pt(II) complexes with aggregate‐induced phosphorescence enhancement are yet to be demonstrated in organic LETs, full electrode emission has been reported for organic LETs based on a red Pt(hopmq)(acac) blend film, in addition to a high electron mobility of 1.3 ± 0.1 cm 2 V −1 s −1 and ON/OFF ratio of 4 ± 1 × 10 6 (Figure ) . Although, phosphorescent emitters have a great potential in push exciton‐light efficiency further, they also have a key drawback—that is these transition metals are often expensive.…”

Section: Let Materialsmentioning

confidence: 99%

Organic Light‐Emitting Transistors: Advances and Perspectives

Chaudhry

Muhieddine

Wawrzinek

et al. 2019

Adv Funct Materials

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The rapid development of charge transporting and light-emitting organic materials in the last decades has advanced device performance, highlighting the high potential of light-emitting transistors (LETs). Demonstrated for the first time over 15 years ago, LETs have transformed from an optoelectronic curiosity to a serious competitor in the race for cheaper and more efficient displays, also showing promise for injection lasers. Thus, what is an LET, how does it work, and what are the current challenges for its integration into mainstream technologies? Herein, some light is shed on these questions. This work also provides the fundamental working principle of LETs, materials that have been used, and device physics and architectures involved in the progression of LET technology. The state-of-the-art development of LETs is also explored as prospect avenues for the future of research and applications in this area.

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“…Given that ZTO work function is −4.9 eV, PEIE (ethoxylated polyethylenimine, 10 nm) was used as work function modification layer to improve electron injection process. [ 19 ] A 110 nm thick light‐emitting layer of mCBP:ACRXTN blend was spin‐coated on top of the PEIE without thermal annealing. Drain contact was formed by thermal evaporation of molybdenum oxide (MoO x , 5 nm) and gold (Au, 15 nm) as the respective thickness of MoO x and Au has been previously reported to exhibit reasonable transmittance of around 60%.…”

Section: Figurementioning

confidence: 99%

High EQE and High Brightness Solution‐Processed TADF Light‐Emitting Transistors and OLEDs

Ahmad

Sobuś

Bencheikh

et al. 2020

Advanced Optical Materials

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Thermally activated delayed fluorescence (TADF) emitters can exhibit high quantum efficiencies by harvesting triplet excitons through efficient reverse intersystem crossing. Reports on efficient TADF based light‐emitting field‐effect transistors (LEFETs) are rare. Moreover, despite efficient TADF organic light‐emitting diodes (OLEDs), most devices have thermally evaporated multilayer device designs. In this work, highly efficient solution processed LEFETs using ACRXTN [3‐(9,9‐dimethylacridin‐10(9H)‐yl)‐9H‐xanthen‐9‐one] are demonstrated to show high external quantum efficiencies (EQEs) of ≈1% and on/off ratios (≈105) at low operating voltages (≈22 V) with negligible EQE roll‐off even at ≈1,500 cd m–2. The same emitter is further studied in solution‐processedOLEDs with a simple architecture to achieve high peak EQEs (≈16%) and brightness (>1000 cd m–2). The OLEDs retain a high EQE (≈10%) at 20 000 cd m–2, indicating excellent charge balance even with such simple device architecture. Our optical simulations identify EQE discrepancy in the two devices, mainly arisen from a poorer light out‐coupling efficiency in the LEFETs (0.8%) than that (≈24%) in the OLEDs. This work shows state‐of‐the‐art of solution‐processed TADF LEFETs and OLEDs with simple device architectures and negligible EQE roll‐off.

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Orange‐Red‐Light‐Emitting Field‐Effect Transistors Based on Phosphorescent Pt(II) Complexes with Area Emission

Cited by 16 publications

References 51 publications

Overlapping‐Gate Organic Light‐Emitting Transistors

Overlapping‐Gate Organic Light‐Emitting Transistors

Organic Light‐Emitting Transistors: Advances and Perspectives

High EQE and High Brightness Solution‐Processed TADF Light‐Emitting Transistors and OLEDs

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