Fundamental limitations for electroluminescence in organic dual-gate field-effect transistors

Shape-Dependent Optical Waveguides and Low-Threshold Lasers from Polymorphic Two-Dimensional Organic Single Crystals

Organic single crystals (OSCs) with uniform morphologies and highly ordered molecular aggregations are promising for high-performance optoelectronic devices, such as organic solid-state lasers (OSSLs), organic light-emitting transistors (OLETs), and organic light-emitting diodes (OLEDs). However, manipulating OSC morphologies and aggregation is challenging. In this study, we synthesized two-dimensional (2D) OSCs of 4,4'-bis[(N-carbazole)styryl]biphenyl (BSBCz) in hexagonal and parallelogram microplate (H-MP and P-MP) forms. Both types exhibit H-aggregation in the 2D plate plane but with different molecular transition dipole moment (TDM) orientations. This leads to different photon coupling modes with H-MP and P-MP microcavities. H-MPs enable isotropic 2D-waveguiding, forming whispering gallery mode (WGM) resonators, while P-MPs create unidirectional waveguiding, forming Fabry-Pérot mode (FP) resonators. These resonators can generate low-threshold laser emissions at 467 and 473 nm, respectively, and exhibit superior lasing stability with a half-life exceeding 2 h. Our BSBCz microplate OSCs are attractive candidates to combine controlled organic microcavities with photon transporting for realizing future integrated optoelectronic devices.

Performance improvement for organic light emitting diodes by changing the position of mixed-interlayer

Organic Light-Emitting Diode (OLED) is presently the most sought-after display technology. It provides low-cost, flexible, rollable displays in addition to wide viewing angles and excellent colour qualities. Still, the organic displays have not reached at their best performance and there is a lot of scope for improvement in their performance. In addition to the injection layer, emission layer, transport layer, etc, researchers are looking forward to the charge carrier transport layer, spacer layer, mixed interlayer, etc. to further enhance the device performance. In this article, a depth analysis related to the impact of the position of the mixed interlayer is performed to analyze the impact on device performance. It is observed that on shifting mixed interlayer (MI) towards the cathode; luminescence and current density depict depreciation. However, on shifting MI towards anode there is a significant performance improvement. The complete analysis includes seven device structures, wherein the position of MI is varied. The best performing device depicts luminescence of 17139 cd/m2 and a current density of 84.6 mA/cm2, which is 40.05% higher for luminescence and 111.5% for current density than that of reference device. Additionally, the internal analysis of device structure is thoroughly evaluated using the cut line method to better understand the internal device physics in terms of the electric field, electron concentration, total current density, Langevin’s recombination rate, and Singlet exciton density.

Analysis of electrical characteristics and electroluminescent efficiency of field induced contact-DGOLET

This research paper discusses the significance development in field-induced contact dual-gate organic light emitting transistor (FIC-DGOLET) device architecture and characteristics. The device behaviour is analyzed and observed significant value of electroluminescent efficiency. The deep investigation of FIC-DGOLET device is discussed in this paper, where impact of varying the various parameters such as thickness of organic semiconductor (OSC) materials from the range of 400 nm to 200 nm at altered value of threshold voltage by using 2D ATLAS simulator. Its theoretical calculation influence over the dynamic control of the device characteristics such as saturated drain current (I ds ), mobility (μ), threshold voltage (V th ) as well as sub threshold swing. The FIC-DGOLET is a dual-gate transistor which also emits light by the operations of two accumulated regions, that are electrons and holes which is not completely overlapped to each other. The leakage current in DG-OLET can be reduced to the extent that 70% than single gate OLET (SG-OLET). The recombination zone mechanism of FIC-DGOLET plays a vital role in its performance, where we get comparable value of electroluminescent efficiency with reported, low value of exciton quenching and current densities. The extracted parameters of DG-OLETs are like drive current of 100A, I on/off 108, threshold voltage V th of 1.3 V at V gs of –3 V and V ds of 0 to –3 V. These extracted performance parameters are very helpful in designing of flexible display applications.

Tunable Linearity of High-Performance Vertical Dual-Gate vdW Phototransistors

Layered 2D semiconductors have been widely exploited in photodetectors due to their excellent electronic and optoelectronic properties. To improve their performance, photogating, photoconductive, photovoltaic, photothermoelectric, and other effects have been used in phototransistors and photodiodes made with 2D semiconductors or hybrid structures. However, it is difficult to achieve the desired high responsivity and linear photoresponse simultaneously in a monopolar conduction channel or a p-n junction. Here, dual-channel conduction with ambipolar multilayer WSe₂ is presented by employing the device concept of dual-gate phototransistor, where p-type and n-type channels are produced in the same semiconductor using opposite dual-gating. It is possible to tune the photoconductive gain using a vertical electric field, so that the gain is constant with respect to the light intensity-a linear photoresponse, with a high responsivity of ≈2.5 × 10⁴ A W^-1 . Additionally, the 1/f noise of the device is kept at a low level under the opposite dual-gating due to the reduction of current and carrier fluctuation, resulting in a high detectivity of ≈2 × 10¹³ Jones in the linear photoresponse regime. The linear photoresponse and high performance of the dual-gate WSe₂ phototransistor offer the possibility of achieving high-resolution and quantitative light detection with layered 2D semiconductors.

Dual-gate organic phototransistor with high-gain and linear photoresponse

The conversion of light into electrical signal in a photodetector is a crucial process for a wide range of technological applications. Here we report a new device concept of dual-gate phototransistor that combines the operation of photodiodes and phototransistors to simultaneously enable high-gain and linear photoresponse without requiring external circuitry. In an oppositely biased, dual-gate transistor based on a solution-processed organic heterojunction layer, we find that the presence of both n- and p-type channels enables both photogenerated electrons and holes to efficiently separate and transport in the same semiconducting layer. This operation enables effective control of trap carrier density that leads to linear photoresponse with high photoconductive gain and a significant reduction of electrical noise. As we demonstrate using a large-area, 8 × 8 imaging array of dual-gate phototransistors, this device concept is promising for high-performance and scalable photodetectors with tunable dynamic range.