Organic light-emitting transistors, three-terminal devices combining a thin-film transistor with a light-emitting diode, have generated increasing interest in organic electronics. However, increasing ...their efficiency while keeping the operating voltage low still remains a key challenge. Here, we demonstrate organic permeable base light-emitting transistors; these three-terminal vertical optoelectronic devices operate at driving voltages below 5.0 V; emit in the red, green and blue ranges; and reach, respectively, peak external quantum efficiencies of 19.6%, 24.6% and 11.8%, current efficiencies of 20.6 cd A
, 90.1 cd A
and 27.1 cd A
and maximum luminance values of 9,833 cd m
, 12,513 cd m
and 4,753 cd m
. Our simulations demonstrate that the nano-pore permeable base electrode located at the centre of the device, which forms a distinctive optical microcavity and regulates charge carrier injection and transport, is the key to the good performance obtained. Our work paves the way towards efficient and low-voltage organic light-emitting transistors, useful for power-efficient active matrix displays and solid-state lighting.
Abstract
Devices made using thin-film semiconductors have attracted much interest recently owing to new application possibilities. Among materials systems suitable for thin-film electronics, organic ...semiconductors are of particular interest; their low cost, biocompatible carbon-based materials and deposition by simple techniques such as evaporation or printing enable organic semiconductor devices to be used for ubiquitous electronics, such as those used on or in the human body or on clothing and packages
1–3
. The potential of organic electronics can be leveraged only if the performance of organic transistors is improved markedly. Here we present organic bipolar transistors with outstanding device performance: a previously undescribed vertical architecture and highly crystalline organic rubrene thin films yield devices with high differential amplification (more than 100) and superior high-frequency performance over conventional devices. These bipolar transistors also give insight into the minority carrier diffusion length—a key parameter in organic semiconductors. Our results open the door to new device concepts of high-performance organic electronics with ever faster switching speeds.
Abstract
The main advantage of organic transistors with dual gates/bases is that the threshold voltages can be set as a function of the applied second gate/base bias, which is crucial for the ...application in logic gates and integrated circuits. However, incorporating a dual gate/base structure into an ultra-short channel vertical architecture represents a substantial challenge. Here, we realize a device concept of vertical organic permeable dual-base transistors, where the dual base electrodes can be used to tune the threshold voltages and change the on-currents. The detailed operation mechanisms are investigated by calibrated TCAD simulations. Finally, power-efficient logic circuits, e.g. inverter, NAND/AND computation functions are demonstrated with one single device operating at supply voltages of <2.0 V. We believe that this work offers a compact and technologically simple hardware platform with excellent application potential for vertical-channel organic transistors in complex logic circuits.
In state‐of‐the‐art organic transistors, the transit frequency fT is reported to be fT = 40 MHz for vertical organic transistors, where a voltage‐normalized fT corresponds to 0.36 MHz V−2. The ...reported highest fT for conventional organic transistors is fT = 160 MHz, where the voltage‐normalized fT is 0.1 MHz V−2. While the reported transit frequency fT of n‐MOSFETs for silicon technology when normalized by the applied biases exceeds 300 GHz V−2. The reported carrier mobility of organic semiconductors is over 100 cm2 V−1 s−1, which is almost an order of magnitude lower than that of silicon. However, the transit frequency fT of organic transistors lags far behind silicon technology by about six orders of magnitude at a comparable device length below 300 nm. In this work, a technology computer‐aided design (TCAD) simulator is adjusted to the experimental DC and AC characteristics of the 200 nm device length vertical organic permeable‐base transistors (OPBTs) based on C60 as semiconductor. The AC performance of the devices is investigated and quantitatively analyzed the influence and contribution of key design, structure and material parameters that determine fT and fmax. The feasible ways to enhance and optimize the highest achievable fT and fmax are identified to reach the GHz−range$\rm GHz-range$ and overcome the limitations to high‐frequency operation in organic transistors.
This research investigates the capabilities of organic transistors to achieve gigahertz (GHz) frequencies. The study focuses on improving the design of the device and addressing key parameters to enhance the AC performance of vertical organic permeable‐base transistors. The results indicate potential pathways for high‐frequency operation in organic transistors, offering new possibilities in the field of high‐speed electronics.
A closed-form and physics-based compact model is presented for calculating the DC characteristics of Schottky barrier field-effect transistors and dual gated reconfigurable field-effect transistors. ...The given model calculates the charge-carrier injection over the Schottky barriers. This current is separated into a field emission current, given by charge carriers tunneling through the Schottky barriers and a thermionic emission current, given by charge carriers overcoming the Schottky barriers. The model verification is done by comparing the model results to measurements and TCAD simulations.
In this work, we investigate organic electrochemical transistors (OECTs) as a novel artificial electronic device for the realization of synaptic behavior, bioelectronics, and a variety of ...applications. A numerical method considering the Poisson-Boltzmann statistics is introduced to reproduce associated charge densities, electrostatics and switching properties of OECTs. We shed light on the working principle of OECTs by taking into account the ionic charge distribution in the electrolyte and incomplete ionization of the organic semiconductor describing the underlying electrochemical redox reaction. This enables analyzing the OECTs electrical performance as well as a simplified chemical properties via an electrical double layer, doping and de-doping of the OMIEC layer. We have fabricated, characterized, simulated and analyzed OECTs based on PEDOT:PSS, and we show that the proposed model reveals important properties of the device's working mechanism. The model shows a good agreement with the experimental data of the fabricated devices.
This paper presents a compact model for organic thin-film transistors fabricated in the staggered or coplanar device architecture which includes short-channel effects related to the potential barrier ...in the channel region, which manifest themselves as threshold voltage roll-off, drain-induced barrier lowering, and subthreshold swing degradation. Furthermore, the effect of non-linear injection due to a work-function mismatch between the source/drain contacts and the semiconductor is considered. The model includes a charge-based capacitance model considering overlap and fringing regions in short-channel multi-finger layout structures. Extensions include a model for drain-current variability, low-frequency noise and non-quasistatic effects. The introduction of physically meaningful fitting parameters provides a high degree of flexibility to the model. The equation package is verified using the results of measurements performed on transistors fabricated on flexible substrates and is available in Verilog-A for an efficient circuit simulation on different design platforms.
An accurate and efficient noise-based simulation technique for predicting the impact of device-parameter variability on the DC statistical behavior of integrated circuits is presented. The proposed ...method is validated on a source follower, a diode-load inverter and a current mirror based on organic thin-film transistors. Taking advantage of the standard noise analysis of a circuit, after translating the statistical variation of the electrical parameters of the transistors into equivalent-noise circuit components, the proposed technique yields results identical to those obtained from a Monte Carlo simulation, but in a significantly shorter amount of time.
This journal paper introduces a charge-based approach for the calculation of charges and capacitances in staggered organic thin-film transistors (OTFTs). Based on an already existing DC model, the ...charges are yielded in an analytical and compact form. A linear charge partitioning scheme is applied to ascribe charges to the drain/source side of the channel. The final equation is only dependent on geometrical parameters and the charge densities at the drain/source end of the channel. Furthermore, the fringing regions in fabricated devices are taken into account. The compact model is implemented in Verilog-A and the capacitances are compared to Sentaurus TCAD simulation results as well as measurement data. Additionally, simulation results for a differential amplifier are compared to measurements. The advantage of this model is its unique formulation covering all operation regimes.
An analytical approach for modeling the electrostatic potential in nanoscale undoped FinFETs is derived. This method uses a 2-D solution for this potential within a double-gate FET and takes into ...account the top gate electrode as the third dimension by applying the conformal mapping technique. Herewith, an analytical closed-form model for the height of the potential barrier below threshold is defined which includes 3-D effects. From that, models for subthreshold slope and threshold voltage of nanoscale triple-gate FETs are derived. The results are in good agreement with numerical device simulation results and measurements for channel lengths down to 20 nm.
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