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Porous aromatic frameworks (PAFs)membranes hold great promise for lithium extraction from salt lakes owing to their tunable pore structure and ease of functionalization. Yet, simultaneously achieving high ion selectivity and transport efficiency remains a major challenge. Herein, we report a series of free-standing, continuous porous aromatic framework (PAF) membranes fabricated via surface-initiated polymerization, featuring pre-anchored functional moieties of varied types and lengths. Notably, the ethoxy functionalized variant (PAF-3EO) exhibits exceptional lithium selectivity (Li⁺/Mg²⁺ = 887.9) alongside a high Li⁺ flux (31.5 mol m⁻² h⁻¹). Molecular dynamics simulations attribute this performance to the influence of ethoxy group density on pore dimensions, ion coordination, and dehydration dynamics. This work overcomes the long-standing trade-off between selectivity and permeability, offering a new design paradigm for advanced lithium separation and other ion-selective membrane technologies.

The light-emitting electrochemical cell (LEC) is a good fit for scalable ambient-air coating and printing, since it can deliver efficient emission from a robust three-layer architecture comprising solely air-stable and soluble materials. However, a drawback is that hitherto employed emitters for printed LECs are either conjugated polymers that are efficiency and purification limited or small molecules that are difficult to solution process into uniform thin films. The recent advent of dendrimers that emit by thermally activated delayed fluorescence (TADF) promises to address all these issues, since they can efficiently utilize all (both singlet and triplet) excitons for the light emission, be of high purity because of their well-defined structure, and feature high solubility and good film-forming capacity by the virtue of being equipped with branched dendrons. Herein, an asymmetric second-generation TADF-dendrimer, tBuCz2m2pTRZ, is combined with an ionic-liquid electrolyte for the formulation of a tuned ink, which is used for a bar-coating fabrication of uniform LEC active-material films featuring a high photoluminescence quantum yield of 84%. This opportunity is ultimately utilized for the pioneering demonstration of a bar-coated TADF-dendrimer-LEC, which delivers uniform and bright green luminance of 350 cd m−2 at an external quantum efficiency of 1.2%.

Emissive carbon dots (CDs) that are synthesized from biomass can be highly sustainable, but the number of reported biomass-derived CDs that emit in the ultraviolet (UV) range is small. Moreover, current commercial UV-emitting materials rely heavily on the use of non-sustainable resources, such as rare metals, heavy metals, and petroleum chemicals. This yields that the development of efficient biomass-derived UV-CDs is desired. Here, we report on the hydrothermal conversion of a common green-tea extract (Polyphenon 60) into UV-CDs, which feature a photoluminescence (PL) peak wavelength of 384 nm, a full width at half maximum of 72 nm, and a photoluminescence quantum yield (PLQY) of 17% in water. By shifting to a lower-polarity solvent of 3-phenoxyanisole, the PLQY is strongly enhanced to 81%, and the PL peak blue-shifts to 370 nm, while the maximum solubility is lowered. These observations support the notion that the UV-CDs feature aggregation-induced emission and that they are endowed with hydrophilic surface groups. Moreover, the findings of excitation-wavelength-independent PL and a nanosecond-level short emission lifetime reveal that it is a single distinct fluorophore that produces the UV emission. We finally report preliminary results that the UV-CDs exhibit potential for inhibiting the proliferation of cancer cells.

Light-emitting electrochemical cells (LECs) are promising candidates for fully solution-processed lighting applications because they can comprise a single active-material layer and air-stable electrodes. While their performance is often claimed to be independent of the electrode material selection due to the in situ formation of electric double layers (EDLs), we demonstrate conceptually and experimentally that this understanding needs to be modified. Specifically, the exciton generation zone is observed to be affected by the electrode work function. We rationalize this finding by proposing that the ion concentration in the injection-facilitating EDLs depends on the offset between the electrode work function and the respective semiconductor orbital, which in turn influences the number of ions available for electrochemical doping and hence shifts the exciton generation zone. Further, we investigate the effects of the electrode selection on exciton losses to surface plasmon polaritons and discuss the impact of cavity effects on the exciton density. We conclude by showing that we can replicate the measured luminance transients by an optical model which considers these electrode-dependent effects. As such, our findings provide rational design criteria considering the electrode materials, the active-material thickness, and its composition in concert to achieve optimum LEC performance.

Organic semiconductors that deliver emission with a wavelength exceeding 900 nm can enable a wide range of applications, but the unfortunate fact is that only a small number of such emitters have been synthesized and have demonstrated emissive function in devices. Here, this issue is addressed through the design and synthesis of two terpolymers that comprise a low energy-gap thiophene-thiadiazolobenzotriazole (TBTzTD) donor–acceptor unit as the minority guest incorporated in a majority donor–acceptor conjugated copolymer host, being either thiophene-quinoxaline (TQ) or thiophene-difluoroquinoxaline (TQ2F). These terpolymers are further endowed with high solubility in benign hydrophilic solvents through the grafting of branched oligo(ethylene glycol) side chains onto the quinoxaline unit. The application function of the terpolymer emitters is demonstrated through their implementation in light-emitting electrochemical cells (LECs). It is notable from a sustainability perspective that the emitter is metal free and that the single-layer LEC active material is cast from an environmentally benign water:ethanol solvent blend. From an application perspective, it is attractive that the terpolymer-LEC devices feature a very fast turn-on to significant radiance at low voltage and that they deliver emission with a peak wavelength of 935 nm with TQ-TBTzTD as the emitter and 950 nm with TQ2F-TBTzTD as the emitter.

The attainment of white emission from a light-emitting electrochemical cell (LEC) is important, since it enables illumination and facile color conversion from devices that can be cost-efficient and sustainable. However, a drawback with current white LECs is that they either employ non-sustainable metals as an emitter constituent or are intrinsically efficiency limited by that the emitter only converts singlet excitons to photons. Organic compounds that emit by thermally activated delayed fluorescence (TADF) can address these issues since they can harvest all excitons for light emission while being metal free. Here, we report on the first white LEC based on solely metal-free TADF emitters, as accomplished through careful tuning of the energy-transfer processes and the electrochemically formed doping structure in the single-layer active material. The designed TADF-LEC emits angle-invariant white light (color rendering index = 88) with an external quantum efficiency of 2.1 % at a luminance of 350 cd/m².

Carbon dots (CDs) are an emerging class of nanomaterials with attractive optical properties, which promise to enable a variety of applications. An important and timely question is whether CDs can become a functional and sustainable alternative to incumbent optical nanomaterials, notably inorganic quantum dots. Herein, the current CD literature is comprehensively reviewed as regards to their synthesis and function, with a focus on sustainability aspects. The study quantifies why it is attractive that CDs can be synthesized with biomass as the sole starting material and be free from toxic and precious metals and critical raw materials. It further describes and analyzes employed pretreatment, chemical-conversion, purification, and processing procedures, and highlights current issues with the usage of solvents, the energy and material efficiency, and the safety and waste management. It is specially shown that many reported synthesis and processing methods are concerningly wasteful with the utilization of non-sustainable solvents and energy. It is finally recommended that future studies should explicitly consider and discuss the environmental influence of the selected starting material, solvents, and generated byproducts, and that quantitative information on the required amounts of solvents, consumables, and energy should be provided to enable an evaluation of the presented methods in an upscaled sustainability context.

Understanding “efficiency roll-off” (i.e., the drop in emission efficiency with increasing current) is critical if efficient and bright emissive technologies are to be rationally designed. Emerging light-emitting electrochemical cells (LECs) can be cost- and energy-efficiently fabricated by ambient-air printing by virtue of the in situ formation of a p-n junction doping structure. However, this in situ doping transformation renders a meaningful efficiency analysis challenging. Herein, a method for separation and quantification of major LEC loss factors, notably the outcoupling efficiency and exciton quenching, is presented. Specifically, the position of the emissive p-n junction in common singlet-exciton emitting LECs is measured to shift markedly with increasing current, and the influence of this shift on the outcoupling efficiency is quantified. It is further verified that the LEC-characteristic high electrochemical-doping concentration renders singlet-polaron quenching (SPQ) significant already at low drive current density, but also that SPQ increases super-linearly with increasing current, because of increasing polaron density in the p-n junction region. This results in that SPQ dominates singlet-singlet quenching for relevant current densities, and significantly contributes to the efficiency roll-off. This method for deciphering the LEC efficiency roll-off can contribute to a rational realization of all-printed LEC devices that are efficient at highluminance.

Multiresonant thermally activated delayed fluorescence (MR-TADF) emitters have been the focus of extensive design efforts as they are recognized to show bright, narrowband emission, which makes them very appealing for display applications. However, the planar geometry and relatively large singlet–triplet energy gap lead to, respectively, severe aggregation-caused quenching (ACQ) and slow reverse intersystem crossing (RISC). Here, a design strategy is proposed to address both issues. Two MR-TADF emitters triphenylphosphine oxide (TPPO)-tBu-DiKTa and triphenylamine (TPA)-tBu-DiKTa have been synthesized. Twisted ortho-substituted groups help increase the intermolecular distance and largely suppress the ACQ. In addition, the contributions from intermolecular charge transfer states in the case of TPA-tBu-DiKTa help to accelerate RISC. The organic light-emitting diodes (OLEDs) with TPPO-tBu-DiKTa and TPA-tBu-DiKTa exhibit high maximum external quantum efficiencies (EQEmax) of 24.4% and 31.0%, respectively. Notably, the device with 25 wt% TPA-tBu-DiKTa showed both high EQEmax of 28.0% and reduced efficiency roll-off (19.9% EQE at 1000 cd m−2) compared to the device with 5 wt% emitter (31.0% EQEmax and 11.0% EQE at 1000 cd m−2). The new emitters were also introduced into single-layer light-emitting electrochemical cells (LECs), equipped with air-stable electrodes. The LEC containing TPA-tBu-DiKTa dispersed at 0.5 wt% in a matrix comprising a mobility-balanced blend-host and an ionic liquid electrolyte delivered blue luminance with an EQEmax of 2.6% at 425 cd m−2. The high efficiencies of the OLEDs and LECs with TPA-tBu-DiKTa illustrate the potential for improving device performance when the DiKTa core is decorated with twisted bulky donors.

It is crucial to develop functional electronic materials that can be processed from green solvents to achieve environmentally sustainable and cost-efficient printing fabrication of organic electronic devices. Here, the design and cost-efficient synthesis of two hydrophilic and emissive conjugated polymers, TQ-OEG and TQ2F-OEG, are presented, which are rendered hydrophilic through the grafting of oligo(ethylene glycol) (OEG) solubilizing groups onto the thiophene-quinoxaline conjugated backbone and thereby can be processed from a water:ethanol solvent mixture. It is shown that the introduction of the OEG groups enables for a direct dissolution of salts by the neat polymer for the attainment of solid-state ion mobility. These properties are utilized for the design and development of light-emitting electrochemical cells (LECs), the active materials of which can be solution cast from a water:ethanol-based ink. It is specifically shown that such an LEC device, comprising an optimized blend of the TQ2F-OEG emitter and a Li salt as the active material positioned between two air-stabile electrodes, delivers deep-red emission (peak wavelength = 670 nm) with a radiance of 185 µW m⁻² at a low drive voltage of 2.3 V. This study contributes relevant information as to how polymers and LEC devices can be designed and fabricated to combine functionality with sustainability.