A light emitting transistor based on a hybrid metal oxide-organic semiconductor lateral heterostructure
TL;DR: A light-emitting field effect transistor (LEFET) was fabricated in this paper, with its architecture based on a distinct heterojunction located midway between the source and drain contacts.
Abstract: A light-emitting field-effect transistor was fabricated, with its architecture based on a distinct heterojunction located midway between the source and drain contacts. Tetracene enabled hole transport on one side of the heterojunction (hole mobility ∼0.071 cm2/Vs), while amorphous solution-processed zinc tin oxide supported electron transport on the other side (electron mobility ∼0.81 cm2/Vs). The drain current vs. gate voltage curves of this device have a bell-shaped profile that is characteristic of lateral heterojunction bipolar field-effect transistors. The green light emission—from tetracene—closely follows the trend in drain current and is naked-eye visible in a darkened room.
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TL;DR: This review article summarizes the recent advancements on OLETs in light of materials, device configurations, operation conditions, etc and intends to provide readers with a deeper understanding of the design of future Olets.
Abstract: Organic light-emitting transistors (OLETs) represent an emerging class of organic optoelectronic devices, wherein the electrical switching capability of organic field-effect transistors (OFETs) and the light-generation capability of organic light-emitting diodes (OLEDs) are inherently incorporated in a single device. In contrast to conventional OFETs and OLEDs, the planar device geometry and the versatile multifunctional nature of OLETs not only endow them with numerous technological opportunities in the frontier fields of highly integrated organic electronics, but also render them ideal scientific scaffolds to address the fundamental physical events of organic semiconductors and devices. This review article summarizes the recent advancements on OLETs in light of materials, device configurations, operation conditions, etc. Diverse state-of-the-art protocols, including bulk heterojunction, layered heterojunction and laterally arranged heterojunction structures, as well as asymmetric source-drain electrodes, and innovative dielectric layers, which have been developed for the construction of qualified OLETs and for shedding new and deep light on the working principles of OLETs, are highlighted by addressing representative paradigms. This review intends to provide readers with a deeper understanding of the design of future OLETs.
157 citations
TL;DR: Using a novel combination of device architecture and materials a bilayer device comprised of an inorganic and organic semiconducting layer is fabricated and the optoelectronic properties are presented.
Abstract: Light emitting fi eld-effect transistors (LEFETs) are an emerging class of multifunctional optoelectronic device. LEFETs combine the switching abilities of a fi eld-effect transistor (FET) with the light emitting ability of an OLED. This is particularly the case for unipolar LEFETs as the switching ability is often lower for ambipolar LEFETs where the gate voltage is less able to switch off the current fl ow. This combination of functionality has the potential to simplify circuitry for new applications such as pixels for displays, sensors, and optoelectronic devices in communications.Furthermore, it can provide a platform for studying the optoelectronic properties of organic semiconducting materials. So far, single layer organic LEFETs have been fabricated using polymers, evaporated small organic molecules and single crystals. In these devices there is often a trade-off between the charge mobilities (both electron and holes) and the external quantum effi ciency (EQE). For example, tetracene has a high mobility but low EQE in an LEFET whereas MEHPPV has a lower mobility but a higher effi ciency. A strong disadvantage of these devices is that the highest effi ciencies are generally measured at the lowest brightnesses. These problems have been partially addressed in second generation LEFETs by using two layer devices, one being a high-mobility charge transport layer and the other comprised of an emissive material. These devices have yielded much higher brightnesses, >5000 cd m- 2 , at similar EQEs (0.13%). The use of dendrimer-based materials as emissive layers has yielded similar effi ciencies with the advantage of harvesting the emission from both singlet and triplet excitations. A further feature of the bilayer strategy is that with the correct choice of materials it is possible to tune the colour by varying the voltage, a feature that could be useful for commercialization of LEFETs. However, the majority of hetero-structure (bi-layer) LEFETs operate in the unipolar p-channel regime in which the holes move across the transistor channel and electrons are injected into emissive layer by the low work-function metal electrode, with the emission occurring close to this latter electrode. n-type hetero-structure LEFETs are much more diffi cult to achieve with organic semiconducting materials due to the shortage of high-mobility n-type organic semiconductors and quenching of the electroluminescence by the n-type charge transporting layer.
71 citations
TL;DR: In this paper, the fundamental working principle of light-emitting transistors, materials that have been used, and device physics and architectures involved in the progression of LET technology are discussed.
Abstract: 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.
53 citations
TL;DR: A new HLET design is presented with increased aperture ratio, and optical and electrical characteristics are shown.
Abstract: Area emission is realized in all-solution-processed hybrid light-emitting transistors (HLETs). A new HLET design is presented with increased aperture ratio, and optical and electrical characteristics are shown.
35 citations
TL;DR: In this article, the performance of solution and low-temperature processed hybrid light-emitting field effect transistors is enahnced by a new development strategy for manipulation of the work function at the oxide/polymer interface.
Abstract: The performance of solution and low-temperature processed hybrid light-emitting field-effect transistors is enahnced by a new development strategy. The manipulation of the work function at the oxide/polymer interface is presented for achieving high all-round performance in these devices
25 citations
References
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TL;DR: In this article, the use of sputtered, amorphous inorganic semiconductors as robust charge transport layers and demonstrate devices capable of operating at current densities exceeding 3.5 cm−2 with peak brightness of 1,950 cm−m−2 and maximum external electroluminescence efficiency of nearly 0.1%, which represents a 100-fold improvement over previously reported structures.
Abstract: Colloidal quantum dots, with their tunable luminescence properties, are uniquely suited for use as lumophores in light-emitting devices for display technologies and large-area planar lighting1,2,3,4,5,6,7,8,9,10. In contrast to epitaxially grown quantum dots, colloidal quantum dots can be synthesized as highly monodisperse colloids and solution deposited over large areas into densely packed, solid-state multilayers, which have shown promise as efficient optical gain media11. To be a viable platform for colour-tunable electrically pumped lasers, the present-generation quantum-dot LEDs must be modified to withstand the extended, high-current-density operation needed to achieve population inversion. This requirement necessitates a quantum-dot LED design that incorporates robust charge transport layers. Here we report the use of sputtered, amorphous inorganic semiconductors as robust charge transport layers and demonstrate devices capable of operating at current densities exceeding 3.5 A cm−2 with peak brightness of 1,950 Cd m−2 and maximum external electroluminescence efficiency of nearly 0.1%, which represents a 100-fold improvement over previously reported structures8,10. The authors show that metal oxide and colloidal quantum dots can be combined to fabricate monochrome LEDs with a brightness that matches that of the best organic-based quantum-dot LEDs, but with the advantage of improved shelf-life robustness. The reported maximum external electroluminescence efficiency is nearly 0.1%, which represents a 100-fold improvement over previously reported structures
868 citations
TL;DR: In this article, transparent thin-film transistors (TTFTs) with an amorphous zinc tin oxide channel layer formed via rf magnetron sputter deposition are demonstrated.
Abstract: Transparent thin-film transistors (TTFTs) with an amorphous zinc tin oxide channel layer formed via rf magnetron sputter deposition are demonstrated. Field-effect mobilities of 5–15 and 20–50cm2V−1s−1 are obtained for devices post-deposition annealed at 300 and 600°C, respectively. TTFTs processed at 300 and 600°C yield devices with turn-on voltage of 0–15 and −5–5V, respectively. Under both processing conditions, a drain current on-to-off ratio greater than 107 is obtained. Zinc tin oxide is one example of a new class of high performance TTFT channel materials involving amorphous oxides composed of heavy-metal cations with (n−1)d10ns0 (n⩾4) electronic configurations.
778 citations
TL;DR: The concept of using a p-channel/emitter/n-channel trilayer semiconducting heterostructure in OLETs is introduced, providing a new approach to markedly improve OLET performance and address general fundamental optoelectronic and photonic issues.
Abstract: The potential of organic semiconductor-based devices for light generation is demonstrated by the commercialization of display technologies based on organic light-emitting diodes (OLEDs). Nonetheless, exciton quenching and photon loss processes still limit OLED efficiency and brightness. Organic light-emitting transistors (OLETs) are alternative light sources combining, in the same architecture, the switching mechanism of a thin-film transistor and an electroluminescent device. Thus, OLETs could open a new era in organic optoelectronics and serve as testbeds to address general fundamental optoelectronic and photonic issues. Here, we introduce the concept of using a p-channel/emitter/n-channel trilayer semiconducting heterostructure in OLETs, providing a new approach to markedly improve OLET performance and address these open questions. In this architecture, exciton-charge annihilation and electrode photon losses are prevented. Our devices are >100 times more efficient than the equivalent OLED, >2x more efficient than the optimized OLED with the same emitting layer and >10 times more efficient than any other reported OLETs.
538 citations
TL;DR: In this paper, the authors describe the spatial control of the recombination zone in an ambipolar light-emitting organic transistor (AML-EMI) with respect to a single-input single-output (SIMO) circuit.
Abstract: Spatial control of the recombination zone in an ambipolar light-emitting organic transistor
526 citations
TL;DR: The first organic light-emitting field-effect transistor is reported, which comprises interdigitated gold source and drain electrodes on a Si/SiO(2) substrate and a polycrystalline tetracene thin film forming the active layer of the device.
Abstract: We report the first organic light-emitting field-effect transistor. The device structure comprises interdigitated gold source and drain electrodes on a $\mathrm{S}\mathrm{i}/\mathrm{S}\mathrm{i}{\mathrm{O}}_{\mathrm{2}}$ substrate. A polycrystalline tetracene thin film is vacuum sublimated on the substrate forming the active layer of the device. Both holes and electrons are injected from the gold contacts into this layer leading to electroluminescence from the tetracene. The output characteristics, transfer characteristics, and the optical emission properties of the device are reported. A possible mechanism for electron injection is suggested.
522 citations