If electrically pumped lasing in organic semiconductors could be achieved, it would have a wide-ranging impact on many fields, including healthcare, information transmission, and sensing to name a few. However, a major challenge in the development of these devices is overcoming triplet accumulation that leads to the annihilation of the lasing singlet species. The utilization of triplet recycling, whereby triplets are back converted into lasing singlets has emerged as a promising strategy to address this. Herein, high-speed micro-OLEDs incorporating the multi-resonant TADF emitter DABNA-2 are found to exhibit marked performance enhancements upon introduction into a BSBCz host, which serves as an efficient triplet scavenger. This tailored host environment demonstrates a path to low-threshold lasing devices. Using a combination of experiment and numerical modelling, we visualize the build up of the singlets/triplets/polarons within the device identifying key mechanisms that can be used to reduce the lasing threshold. Using this framework, we are able to calculate lasing thresholds for these materials and estimate how far the community is from a lasing device.

AbstractA breakthrough in the fabrication of amorphous Zn‐Sn‐O (ZTO)‐based thin‐film transistors (TFTs) is presented for volatile organic compound (VOC) detection. The incorporation of highly abundant materials offers substantial economic and environmental benefits. However, analyses for the design of a multilayer channel are still limited. This work demonstrates that the chemical environment influences ZTO‐based TFTs' carrier transport properties and can be tailored for detecting specific VOCs, ensuring high specificity in diagnosing life‐threatening conditions through simple breath analysis. A low‐cost, high‐throughput, fully solution‐processed ZTO and ZnO multilayering strategy is adopted. The in‐depth compositional and morphological analyses reveal that low surface roughness, excellent Zn and Sn intermixing, high oxygen vacancy (31.2%), and M‐OH bonding (11.4%) contents may account for the outstanding electrical and sensing performance of ZTO‐ZTO TFTs. Notably, these TFTs achieve near‐zero threshold voltage (2.20 V), excellent switching properties (107), and high mobility (10 cm2V−1s−1). This results in high responsivity to alcohol vapors at low‐voltage operation with peak responsivity for methanol (R = 1.08 × 106) over two orders of magnitude greater than acetone. When miniaturized, these devices serve as easy‐to‐operate sensors, capable of detecting VOCs with high specificity in ambient conditions.

Organic materials offer wide-band emission covering regions of the spectrum unachievable by conventional semiconductors. If electrically pumped lasing could be demonstrated using these materials, many new classes of optical sensors and detectors could be realized leaving a profound impact on society. Devices fabricated from conducting molecules and polymers have already been demonstrated with polaron densities higher than those which theoretically lead to lasing action; however, threshold remains elusive. Herein, a polymer micro-OLED is reported that achieves record room-temperature current densities of 1.5 , however despite this, it is not high enough to reach lasing threshold. Using a combination of nanosecond spectrographic techniques and detailed simulation, the mechanisms inhibiting lasing action is unraveled. It is shown that although as previously thought singlet-triplet annihilation is important in pushing threshold higher, photon absorption by excited triplets is as (if not more) important in inhibiting lasing action. The complex dynamics of singlets, triplets, and free/excited polarons in these disordered materials are visualized; establishing a pathway to overcome these bottlenecks and realise electrically pumped organic lasing action.

Crosslinkers are important for graphene oxide (GO) plates in filtration applications because they help to define and maintain the integrity of the nanoscale structure. GO platelets were dispersed in aqueous solution and crosslinked using a simple "one-pot" process in which multi-amine functional molecules could react with carboxylic acid or epoxy groups of the GO surfaces. Strain-sweep oscillatory rheology enabled a detailed analysis of the reinforcing behaviour of crosslinkers on GO. Flow stress analysis of three different types of reinforced GO composites shows significant increases in the elastic modulus of the GO composites, compared to non-crosslinked GO. Crosslinkers were octaammonium polyhedral oligomeric silsesquioxane, (OA-POSS), a rigid cage, low Mw (0.8 kg/mol) or high Mw (25 kg/mol) chain branched polyethyleneimine, PEI (flexible). Crosslinking with either of the PEI polymers increases the yield stress of GO composites up to 20 times more than the rigid OA-POSS crosslinker, and nearly 170 times more than the non-crosslinked GO. The 'one pot' synthetic route employed in this work shows that maximum levels of reinforcement are relatively insensitive to crosslinker concentration. The yield stress of all three types of composites increases sharply as a function of crosslinker concentration, reaching a broad plateau, before decreasing slightly. The decrease in reinforcement at high concentrations may be attributed to the saturation of available sites on GO nanosheets inhibiting crosslinking. Composites cross- linked in-situ included a significant fraction of water which was excluded under compression. Crosslinked GO samples under compression showed an increase in the elastic modulus consistent with an increase in the effective concentration of composite. GO-coated membranes showed high rejection (up to similar to 90 %) of Rhodamine WT, and the resilience of these membranes was visibly improved with very low crosslinker loadings, 0.2 % w/w with respect to the mass of GO.

Three polymers with general structure (D-A)n were designed and synthetized to investigate the interaction of strong donors and strong acceptors in polymer chain. They are based on different fused thiophenes (1Th: 4,4'-bis(2-ethylhexyl)-cyclopenta[2,1-b:3,4-b’]dithiophene; 2Th: 4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene; 3Th: 4,8-bis(4-fluoro-5-(2-ethylhexyl)-thiophen-2-yl)benzo[1,2-b:4,5-b']bisthiophene) and N,N'-bis(2-ethylhexyl)-1,8:4,5-naphthalenetetracarboxdiimide (NDI). Fused benzo- and cyclopenta-thiophene derivatives were selected because they are known for their strong electron-donating properties. NDI was coupled with them in polymer chain because it is one of the best known electron withdrawing units. Such combination of donor and acceptor units is one of the strategies for obtaining low band gap conjugated polymers with semiconducting properties for many applications. The interaction of donors and acceptors is a key factor determining the properties of such polymers. The electrochemical and spectroscopic measurement were supported by DFT calculations. Moreover, organic field effect transistors (OFET) were fabricated to demonstrate the feasibility of using the newly developed materials in electronic devices.

Thin films of cadmium telluride (CdTe) have attained the attention of researchers due to the potential application in solar cells. However, cost-effective fabrication of solar cells based on thin films along with remarkable efficiency and control over optical properties is still a challenging task. This study presents an analysis of the structural, optical and electrical properties of undoped and Cu-doped CdTe thin films fabricated on ITO coated glass substrates using an electrodeposition process with a focus on practical applications. Electrolytes of cadmium (Cd), tellurium (Te) and copper (Cu) are prepared with a low molarity of 0.1 M. Thin films are deposited by keeping current density in the range of 0.12–0.3 mA/cm2. Copper doping is varied (2-10 wt%) for the optimized sample. X-ray diffraction crystallography indicates that both undoped CdTe and Cu-doped CdTe films crystallize into a dominant hexagonal lattice. Direct energy band gap is observed for both undoped and doped conditions. The study revealed a drop in the optical band gap energy to ∼1.46 eV with the increase in doping (Cu) concentration from 2 to 10 wt%. Increase in mobility and conductivity is observed with the increase in current density of the deposited undoped CdTe thin films. Whereas, Cu doping of 6 wt% produced thin films with acceptable mobility and conductivity for the doped samples. Furthermore, photoluminescence (PL) spectroscopy unveiled a multitude of emission peaks encompassing the visible spectrum, arising from the combination of electrons and holes through both direct and indirect recombination processes. Findings of this study suggest that chemically produced CdTe thin films would be suitable for use as low-cost applications pertaining to solar cells.

AbstractOne of the most fascinating 2D nanomaterials (NMs) ever found is various members of MXene family. Among them, the titanium‐based MXenes, with more than 70% of publication‐related investigations, are comparatively well studied, producing fundamental foundation for the 2D MXene family members with flexible properties, familiar with a variety of advanced novel technological applications. Nonetheless, there are still more candidates among transitional metals (TMs) that can function as MXene NMs in ways that go well beyond those that are now recognized. Systematized details of the preparations, characteristics, limitations, significant discoveries, and uses of the novel M‐based MXenes (M‐MXenes), where M stands for non‐Ti TMs (M = Sc, V, Cr, Y, Zr, Nb, Mo, Hf, Ta, W, and Lu), are given. The exceptional qualities of the 2D non‐Ti MXene outperform standard Ti‐MXene in several applications. There is many advancement in top‐down as well as bottom‐up production of MXenes family members, which allows for exact control of the M‐characteristics MXene NMs to contain cutting‐edge applications. This study offers a systematic evaluation of existing research, covering everything in producing complex M‐MXenes from primary limitations to the characterization and selection of their applications in accordance with their novel features. The development of double metal combinations, extension of additional metal candidates beyond group‐(III–VI)B family, and subsequent development of the 2D TM carbide/TMs nitride/TM carbonitrides to 2D metal boride family are also included in this overview. The possibilities and further recommendations for the way of non‐Ti MXene NMs are in the synthesis of NMs will discuss in detail in this critical evaluation.

Abnormal concentrations of volatile organic compounds (VOCs) in human breathe can be used as disease-specific biomarkers for the non-invasive diagnosis of medical conditions, such as acetone for diabetes. Solution-processed bottom gate top contact metal oxide thin-film transistors (TFTs) are used to detect acetone vapours, as part of a proof-of-concept study. The effect of increasing annealing temperature ( T ) and channel length ( L ) on electrical and sensing performance are explored. Drain current ( I ds ) increases following exposure as acetone undergoes a redox reaction with the adsorbed oxygen species on the semiconductor surface, which results in free electrons being released back into the conduction band. Responsivity ( R ) is maximized at negative bias ( V gs < 0). For L = 50 μm, the peak R of the TFT annealed at 450 °C is three times greater than that of the TFT annealed at 350 °C, with V gs = − 37.5 V and − 33 V, respectively. Graphical abstract

We report on the mechanism of enhancing the luminance and external quantum efficiency (EQE) by developing nanostructured channels in hybrid (organic/inorganic) light-emitting transistors (HLETs) that combine a solution-processed oxide and a polymer heterostructure. The heterostructure comprised two parts: (i) the zinc tin oxide/zinc oxide (ZTO/ZnO), with and without ZnO nanowires (NWs) grown on the top of the ZTO/ZnO stack, as the charge transport layer and (ii) a polymer Super Yellow (SY, also known as PDY-132) layer as the light-emitting layer. Device characterization shows that using NWs significantly improves luminance and EQE (approximate to 1.1% @ 5000 cd m(-2)) compared to previously reported similar HLET devices that show EQE < 1%. The size and shape of the NWs were controlled through solution concentration and growth time, which also render NWs to have higher crystallinity. Notably, the size of the NWs was found to provide higher escape efficiency for emitted photons while offering lower contact resistance for charge injection, which resulted in the improved optical performance of HLETs. These results represent a significant step forward in enabling efficient and all-solution-processed HLET technology for lighting and display applications.

Organic light-emitting field-effect transistors (LEFETs) provide the possibility of simplifying the display pixilation design as they integrate the drive-transistor and the light emission in a single architecture. However, in p-type LEFETs, simultaneously achieving higher external quantum efficiency (EQE) at higher brightness, larger and stable emission area, and high switching speed are the limiting factors for to realise their applications. Herein, we present a p-type polymer heterostructure-based LEFET architecture with electron and hole injection interlayers to improve the charge injection into the light-emitting layer, which leads to better recombination. This device structure provides access to hole mobility of ~2.1 cm2 V−1 s−1 and EQE of 1.6% at a luminance of 2600 cd m−2. Most importantly, we observed a large area emission under the entire drain electrode, which was spatially stable (emission area is not dependent on the gate voltage and current density). These results show an important advancement in polymer-based LEFET technology toward realizing new digital display applications.

Developing highly efficient and stable photoelectrochemical (PEC) water-splitting electrodes via inexpensive, liquid phase processing is one of the key challenges for the conversion of solar energy into hydrogen for sustainable energy production. ZnO represents one the most suitable semiconductor metal oxide alternatives because of its high electron mobility, abundance, and low cost, although its performance is limited by its lack of absorption in the visible spectrum and reduced charge separation and charge transfer efficiency. Here, we present a solution-processed water-splitting photoanode based on Co-doped ZnO nanorods (NRs) coated with a transparent functionalizing metal–organic framework (MOF). The light absorption of the ZnO NRs is engineered toward the visible region by Co-doping, while the MOF significantly improves the stability and charge separation and transfer properties of the NRs. This synergetic combination of doping and nanoscale surface functionalization boosts the current density and functional lifetime of the photoanodes while achieving an unprecedented incident photon to current efficiency (IPCE) of 75% at 350 nm, which is over 2 times that of pristine ZnO. A theoretical model and band structure for the core–shell nanostructure is provided, highlighting how this nanomaterial combination provides an attractive pathway for the design of robust and highly efficient semiconductor-based photoanodes that can be translated to other semiconducting oxide systems.

Hygroscopic insulator field-effect transistors (HIFETs) are a class of low-voltage-operation organic transistors that have been successfully demonstrated for biosensing applications through modification of the gate electrode. However, modification of the gate electrode often leads to nonideal transistor characteristics due to changes in its intrinsic electrical properties. This work investigates the effect of gate conductance in HIFETs using poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) as a model gate electrode. It is revealed that a reduction in gate conductance results in a reduction in the effective gate voltage and plays an important role in defining HIFET characteristics. Key figures of merit, including ON/OFF ratio, threshold voltage, transconductance, and saturation mobility increase with increasing gate conductance and reach a plateau once sufficient gate conductance is attained. This effect is attributed to a decrease in the effective gate voltage along the gate electrode arising from its resistivity when a gate leakage current is present. These results are widely applicable and serve as design rules for HIFET device optimization.

The vast majority of conjugated‐polymer‐based light emitting field‐effect transistors (LEFETs) are characterized by low charge‐carrier mobilities typically in the 10 −5 to 10 −3 cm 2 V −1 s −1 range. Fast carrier transport is a highly desirable characteristic for high‐frequency LEFET operation and, potentially, for use in electrically pumped lasers. Unfortunately, high‐mobility organic semiconductors are often characterized by strong intermolecular π–π interactions that reduce luminescence. Development of new materials and/or device concepts that overcome this hurdle are therefore required. Single organic semiconductor layer based LEFETs that combine high hole mobilities with encouraging light emission characteristics are reported. This is achieved in a single polymer layer LEFET, which is further enhanced through the use of a small‐molecule/conjugated polymer blend system that possesses a film microstructure which supports enhanced charge‐carrier mobility (3.2 cm 2 V −1 s −1 ) and promising light‐emission characteristics (1600 cd m −2 ) as compared to polymer‐only based LEFETs. This simple approach represents an attractive strategy to further advance the performance of solution‐processed LEFETs.

The vast majority of conjugated polymer-based light emitting field-effect transistors (LEFETs) are characterized by low charge carrier mobilities typically in the range 10 to 10 cm V s range. Fast carrier transport is a highly desirable characteristic for high frequency LEFET operation and, potentially, for use in electrically-pumped lasers. Unfortunately, high mobility organic semiconductors are often characterised by strong intermolecular π-π interactions that reduce luminescence. Development of new materials and/or device concepts that overcome this hurdle are therefore required. We report single organic semiconductor layer, light-emitting transistors that combine the highest hole mobilities reported to date for any polymer-based LEFET, with encouraging light emission characteristics. We achieve this in a single polymer layer LEFET, which was further enhanced through the use of a small-molecule/conjugated polymer blend system that possesses a film microstructure which supports enhanced charge carrier mobility (3.2 cm V s) and promising light emission characteristics (1600 cd m) as compared to polymer-only based LEFETs. This simple approach represents an attractive strategy to further advance the performance of solution-processed LEFETs.

We report the development of highly efficient and stable solution-processed organic light-emitting transistors (OLETs) that combine a polymer heterostructure with the transparent high-k dielectric poly(vinylidenefluoride(0.62)-trifluoroethylene(0.31)-chlorotrifluoroethylene(0.7)) (P(VDF-TrFE-CTFE)). The polymer heterostructure comprises of poly[4-(4,4-dihexadecyl-4H-cyclopenta[1,2-b:5,4-b']-dithiophen-2-yl)-alt-[1,2,5]thiadiazolo[3,4-c]pyridine] (PCDTPT) and Super Yellow as charge-transporting and light-emitting layers, respectively. Device characterization shows that the use of P(VDF-TrFE-CTFE) leads to larger channel currents (approximate to 2 mA) and lower operating voltages (-35 V) than for previously reported polymer based OLETs. Furthermore, the combined transparency of the dielectric and gate electrode, results in efficient bottom emission with external quantum efficiency of approximate to 0.88% at a luminance L >= 2000 cd m(-2). Importantly, the resulting OLETs exhibit excellent shelf life and operational stability. The present work represents a significant step forward in the pursuit of all-solution-processed OLET technology for lighting and display applications.

Solution‐processed hybrid organic–inorganic perovskite semiconductors have demonstrated remarkable performance for both photovoltaic and light‐emitting‐diode applications in recent years, launching a new field of condensed matter physics. However, their use in other emerging optoelectronic applications, such as light‐emitting field‐effect transistors (LEFETs) has been surprisingly limited, wth only a few low‐performance devices reported. The development of hybrid LEFETs consisting of a solution‐processed self‐organized multiple‐quantum‐well lead iodide perovskite layer grown onto an electron‐transporting In2O3/ZnO heterojunction channel is reported. The multilayer transistors offer bifunctional characteristics, namely, transistor function with high electron mobility (>20 cm2 V−1 s−1) and a large current on/off ratio (>106), combined with near infrared light emission (λmax = 783 nm) and a promising external quantum efficiency (≈0.2% at 18 cd m−2). A further interesting feature of these hybrid LEFETs, in comparison to previously reported structures, is their highly uniform and stable emission characteristics, which make them attractive for smart‐pixel‐format display applications.

Organic Field Effect Transistors (OFETs) have shown great potential for future electronic technologies due to their low-cost solution processing, mechanical flexibility and potential applications for large area displays. One of the big obstacles in the realization of the practical applications is the inherent poor ambient stability of the OFETs. Here we report on the aging dependent degradation mechanism in the Poly[2,5-(2-octyldodecy1)-3,6-diketopyrrolopyrrole-alt-5,5-(2,5-di(thien-2-yDthieno [3,2-b]thiophene)] (DPPDTT) based OFETs in the ambient conditions. These polymer OFETs showed the charge carrier mobility, threshold voltage and current on/off ratios in the range of 0.2 cm(2)V(-1)s(-1), -15 V and 10(6) respectively. The device parameters showed variations in their values initially and then became stable with aging after similar to 20% initial degradations in the ambient. We have correlated the degradation in the OFET performance parameters with the degradation in the polymer channel layer that is confirmed with a time dependent FTIR spectra. Our findings are thus important to understand and achieve stability in OFET devices by aging them.

We report the development of low operating voltages in inorganic-organic hybrid light-emitting transistors (HLETs) based on a solution-processed ZrO x gate dielectric and a hybrid multilayer channel consisting of the heterojunction In2O3/ZnO and the organic polymer "Super Yellow" acting as n- and p-channel/emissive layers, respectively. Resulting HLETs operate at the lowest voltages reported to-date (<10 V) and combine high electron mobility (22 cm2/(V s)) with appreciable current on/off ratios (≈103) and an external quantum efficiency of 2 × 10-2% at 700 cd/m2. The charge injection, transport, and recombination mechanisms within this HLET architecture are discussed, and prospects for further performance enhancement are considered.

Organic light emitting field effect transistors (LEFETs) integrate light emission of a diode with logic functions of a transistor into a single device architecture. This integration has the potential to provide simplified displays at low costs and access to injection lasing. However, the charge carrier mobility in LEFETs is a limiting factor in realizing high current densities along with a trade-off between brightness and efficiency. Herein, we present a technique controlling the nanoscale morphology of semi-conducting polymers using nanoscale grooved substrates and dip-coating deposition to achieve high current density. We then applied this approach to heterostructure LEFETs and demonstrated brightness exceeding 29000 cd m(-2) at an EQE of 0.4% for a yellow emitter and 9600 cd m(-2) at an EQE of 0.7% for a blue emitter. These results represent a significant advancement in organic optoelectronics and are an important milestone toward the realization of new applications in displays and electrically pumped lasing.