Optically pumped colloidal-quantum-dot lasing in LED-like devices with an integrated optical cavity.

Realization of electrically pumped lasing with solution processable materials will have a revolutionary impact on many disciplines including photonics, chemical sensing, and medical diagnostics. Due to readily tunable, size-controlled emission wavelengths, colloidal semiconductor quantum dots (QDs) are attractive materials for attaining this goal. Here we use specially engineered QDs to demonstrate devices that operate as both a light emitting diode (LED) and an optically pumped laser. These structures feature a distributed feedback resonator integrated into a bottom LED electrode. By carefully engineering a refractive-index profile across the device, we are able to obtain good confinement of a waveguided mode within the QD medium, which allows for demonstrating low-threshold lasing even with an ultrathin (about three QD monolayers) active layer. These devices also exhibit strong electroluminescence (EL) under electrical pumping. The conducted studies suggest that the demonstrated dual-function (lasing/EL) structures represent a promising device platform for realizing colloidal QD laser diodes

Optically pumped colloidal-quantum-dot lasing in LED-like devices with an integrated optical cavity.

Realization of electrically pumped lasing with solution processable materials will have a revolutionary impact on many disciplines including photonics, chemical sensing, and medical diagnostics. Due to readily tunable, size-controlled emission wavelengths, colloidal semiconductor quantum dots (QDs) are attractive materials for attaining this goal. Here we use specially engineered QDs to demonstrate devices that operate as both a light emitting diode (LED) and an optically pumped laser. These structures feature a distributed feedback resonator integrated into a bottom LED electrode. By carefully engineering a refractive-index profile across the device, we are able to obtain good confinement of a waveguided mode within the QD medium, which allows for demonstrating low-threshold lasing even with an ultrathin (about three QD monolayers) active layer. These devices also exhibit strong electroluminescence (EL) under electrical pumping. The conducted studies suggest that the demonstrated dual-function (lasing/EL) structures represent a promising device platform for realizing colloidal QD laser diodes

Solution-processable integrated CMOS circuits based on colloidal CuInSe2 quantum dots.

The emerging technology of colloidal quantum dot electronics provides an opportunity for combining the advantages of well-understood inorganic semiconductors with the chemical processability of molecular systems. So far, most research on quantum dot electronic devices has focused on materials based on Pb- and Cd chalcogenides. In addition to environmental concerns associated with the presence of toxic metals, these quantum dots are not well suited for applications in CMOS circuits due to difficulties in integrating complementary n- and p-channel transistors in a common quantum dot active layer. Here, we demonstrate that by using heavy-metal-free CuInSe2 quantum dots, we can address the problem of toxicity and simultaneously achieve straightforward integration of complimentary devices to prepare functional CMOS circuits. Specifically, utilizing the same spin-coated layer of CuInSe2 quantum dots, we realize both p- and n-channel transistors and demonstrate well-behaved integrated logic circuits with low switching voltages compatible with standard CMOS electronics

Solution-processable integrated CMOS circuits based on colloidal CuInSe2 quantum dots.

The emerging technology of colloidal quantum dot electronics provides an opportunity for combining the advantages of well-understood inorganic semiconductors with the chemical processability of molecular systems. So far, most research on quantum dot electronic devices has focused on materials based on Pb- and Cd chalcogenides. In addition to environmental concerns associated with the presence of toxic metals, these quantum dots are not well suited for applications in CMOS circuits due to difficulties in integrating complementary n- and p-channel transistors in a common quantum dot active layer. Here, we demonstrate that by using heavy-metal-free CuInSe2 quantum dots, we can address the problem of toxicity and simultaneously achieve straightforward integration of complimentary devices to prepare functional CMOS circuits. Specifically, utilizing the same spin-coated layer of CuInSe2 quantum dots, we realize both p- and n-channel transistors and demonstrate well-behaved integrated logic circuits with low switching voltages compatible with standard CMOS electronics

Solution-processable integrated CMOS circuits based on colloidal CuInSe2 quantum dots

Designing efficient toxic-element-free technologies in solution-processable CMOS electronics remains a challenge. Here, the authors demonstrate integrated logic CMOS circuits based on heavy-metal-free colloidal CuInSe2 quantum dots with low switching voltages and with degradation-free performance on month-long time scales

Top-Gate Field-Effect Transistor as a Testbed for Evaluating the Photostability of Organic Photovoltaic Polymers

© 2022 Wiley-VCH GmbHLight-induced performance degradation in organic solar cells (OSCs) is a major impediment to their commercialization. As the photostability of OSCs strongly depends on the material's properties, the most effective solution for this concern is to develop a photostable material. However, the wide variety of causes of photo-instability in a standard multilayered OSC structure complicates the evaluation of photostability of newly developed materials. To address this challenge, a top-gate field-effect transistor (FET) as a testbed for evaluating the photostability of OSC materials is proposed. This device test platform minimizes the internal and external origins of photo-instability by employing a fluoropolymer gate dielectric. The photostability of an OSC material incorporated in this FET testbed can be evaluated by monitoring light-induced mobility degradation. Two types of common donor polymers with similar chemical structures and crystallinity are employed as test materials, and their photostability is evaluated. The test results correspond to the photostability measurements conducted in the standard OSC structure, validating the proposed FET testbed. The proposed FET testbed enables rapid evaluation of the photostability of a newly developed OSC material, thereby providing timely feedback to material scientists. This boosts the development of photostable OSC materials.N

Fluorinated CYTOP passivation effects on the electrical reliability of multilayer MoS2 field-effect transistors

We demonstrated highly stable multilayer molybdenum disulfide (MoS2) field-effect transistors (FETs) with negligible hysteresis gap (Delta V-HYS similar to 0.15 V) via a multiple annealing scheme, followed by systematic investigation for long-term air stability with time (similar to 50 days) of MoS2 FETs with (or without) CYTOP encapsulation. The extracted lifetime of the device with CYTOP passivation in air was dramatically improved from 7 to 377 days, and even for the short-term bias stability, the experimental threshold voltage shift, outstandingly well-matched with the stretched exponential function, indicates that the device without passivation has approximately 25% larger the barrier distribution (Delta E-B = k(B)T(o)) than that of a device with passivation. This work suggests that CYTOP encapsulation can be an efficient method to isolate external gas (O-2 and H2O) effects on the electrical performance of FETs, especially with low-dimensional active materials like MoS2

Highly Stable Organic Transistors on Paper Enabled by a Simple and Universal Surface Planarization Method

In this work, operationally and mechanically stable organic field-effect transistors (OFETs) are demonstrated on aramid fiber-based paper enabled by a simple and universal surface planarization method. By employing a nanoimprint lithography-inspired surface smoothening method, rough aramid paper is successfully smoothened from a scale of several tens of micrometers to a sub-nanometer-scale surface roughness. Owing to the sub-nanometer-scale surface roughness of the aramid paper, the OFETs fabricated on the aramid paper exhibit decent field-effect mobility (0.25 cm(2) V-1 s(-1)) with a high current on-to-off ratio (>10(7)), both of which are comparable with those of OFETs fabricated on rigid silicon substrates. Moreover, the OFETs fabricated on the aramid paper exhibit both high operational and mechanical stability; this is indicated by a bias-stress-induced threshold voltage shift ( increment V-TH approximate to 4.27 V under an excessive gate bias stress of 1.7 MV cm(-1) for 1 h 30 min) comparable to that of OFETs on a rigid silicon substrate, moderate field-effect mobility, and a threshold voltage stability under 1000 bending cycles with a compressive strain of 1%. The demonstration of highly stable OFETs on paper enabled by the simple planarization method will expand the potential use of various types of paper in electronic applications.N

All-Solution-Processed Quantum Dot Light-Emitting Diode Using Phosphomolybdic Acid as Hole Injection Layer

In this study, we investigate phosphomolybdic acid (PMA), which allows solution processing of quantum dot light-emitting diodes. With its low cost, easy solution processes, and excellent physical and optical properties, PMA is a potential candidate as the hole injection layer (HIL) in optoelectronic devices. We evaluate the physical and electrical properties of PMA using various solvents. The surface morphology of the PMA film was improved using a solvent with appropriate boiling points, surface tension, and viscosity to form a smooth, pinhole-free film. The energy level was regulated according to the solvent, and PMA with the appropriate electronic structure provided balanced charge carrier transport in quantum dot electroluminescent (QD-EL) devices with enhanced efficiency. A device using PMA dissolved in cyclohexanone was demonstrated to exhibit improved efficiency compared to a device using PEDOT:PSS, which is a conventional solution HIL. However, the stability of PMA was slightly poorer than PEDOT:PSS; there needs to be further investigation