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Body temperature is critical indicator of human health, and its real‐time monitoring is crucial for assessing body status and disease diagnosis. In this work, a flexible temperature sensor is presented that employs a graphite/polyvinylidene fluoride (PVDF)/polyaniline composite and demonstrates a negative temperature coefficient (NTC). This sensor exhibits high sensitivity (−0.832%/ °C), rapid response time (11.05 s), and excellent linearity (R2 = 0.98). Its integration with a self‐adhesion PDMS‐PEG substrate layer ensures close skin contact, enhancing the accuracy of temperature measurements. Notably, the sensor's stability and resistance to sweat and deformation ensure continuous, reliable temperature monitoring, even during extensive exercise. This sensor thus represents a significant advancement in flexible and waterproof temperature sensing technologies. [ABSTRACT FROM AUTHOR]

Nonfused ring electron acceptors (NFREAs) are promising candidates for future commercialization of organic solar cells (OSCs) due to their simple synthesis. Still, the power conversion efficiencies (PCEs) of NFREA‐based OSCs have large room for improvement. In this work, by merging end group halogenation and side chain engineering, we developed four A–D–A'–D–A type NFREAs, which we refer to as EH‐4F, C4‐4F, EH‐4Cl, and C4‐4Cl. Single crystal X‐ray diffraction revealed that multiple intermolecular S···F interactions between cyclopentadithiophene and 5,6‐difluoro‐3‐(dicyanomethylene)indanone could cause an unfavorable dimer formation, leading to ineffective π–π stackings in EH‐4F and C4‐4F, whereas no such dimer was found in EH‐4Cl and C4‐4Cl after replacing with 5,6‐dichloro‐3‐(dicyanomethylene)indanone. Moreover, although the shorter n‐butyl side chain resulted in a closer molecular packing in C4‐4Cl, EH‐4Cl (2‐ethylhexyl substitution) with proper crystallinity exhibited enhanced face‐on orientation in thin film, which is favorable for vertical charge transport and further reducing charge recombination. As a result, a PCE of 13.0% is obtained for EH‐4Cl‐based OSC with a fill factor of 0.70. This work highlights the importance of molecular packing and orientation control toward future high‐performance A–D–A'–D–A type NFREAs. [ABSTRACT FROM AUTHOR]

The erratic, intermittent, and unpredictable nature of sweat production, resulting from physiological or psychological fluctuations, poses intricacies to consistently and accurately sample and evaluate sweat biomarkers. Skin‐interfaced microfluidic devices that rely on colorimetric mechanisms for semi‐quantitative detection are particularly susceptible to these inaccuracies due to variations in sweat secretion rate or instantaneous volume. This work introduces a skin‐interfaced colorimetric bifluidic sweat device with two synchronous channels to quantify sweat rate and biomarkers in real‐time, even during uncertain sweat activities. In the proposed bifluidic‐distance metric approach, with one channel to measure sweat rate and quantify collected sweat volume, the other channel can provide an accurate analysis of the biomarkers based on the collected sweat volume. The closed channel design also reduces evaporation and resists contamination from the external environment. The feasibility of the device is highlighted in a proof‐of‐the‐concept demonstration to analyze sweat chloride for evaluating hydration status and sweat glucose for assessing glucose levels. The low‐cost yet highly accurate device provides opportunities for clinical sweat analysis and disease screening in remote and low‐resource settings. The developed device platform can be facilely adapted for the other biomarkers when corresponding colorimetric reagents are exploited. [ABSTRACT FROM AUTHOR]

Non-electronic wearables that utilize skin-interfaced microfluidic technology have revolutionized the collection and analysis of human sweat, providing valuable biochemical information and indicating body hydration status. However, existing microfluidic devices often require constant monitoring of data during sweat assessment, thereby impeding the user experience and potentially missing anomalous physiological events, such as excessive sweating. Moreover, the complex manufacturing process hampers the scalability and large-scale production of such devices. Herein, we present a self-feedback microfluidic device with a unique dehydration reminder through a cost-effective "CAD-to-3D device" approach. It incorporates two independent systems for sweat collection and thermal feedback, including serpentine microchannels, reservoirs, petal-like bursting valves and heating chambers. The device operates by sequentially collecting sweat in the channels and reservoirs, and then activating thermal stimulators in the heating chambers through breaking the valves, initiating a chemical exothermic reaction. Human trials validate that the devices effectively alert users to potential dehydration by inducing skin thermal sensations triggered by sweat sampling. The proposed device offers facile scalability and customizable fabrication, and holds promise for managing hydration strategies in real-world scenarios, benefiting individuals engaged in sporting activities or exposed to high-temperature settings. [ABSTRACT FROM AUTHOR]

Recently, numerous efforts have been devoted to sky blue or greenish blue organic light-emitting diodes (OLEDs), nevertheless, the deep blue and pure blue OLEDs still remain a formidable challenge. Herein, a series of deep blue and pure blue donor–acceptor–donor (D–A–D) type emitters, namely Cz-DMTD, PhCz-DMTD and TMCz-DMTD, were constructed. For PhCz-DMTD which exhibited no delayed fluorescence component, the extended delocalization of donors and the enhancement of oscillator strength were both observed through theoretical calculation. For methyl-engineered TMCz-DMTD, the degenerate charge transfer singlet excited (1CT) and triplet excited (3CT) states and localized triplet excited (3LE) state endowed a thermally activated delayed fluorescence (TADF) character. Moreover, PhCz-DMTD and TMCz-DMTD based OLEDs displayed emission with Commission Internationale de l'Eclairage (CIE) coordinates of (0.164, 0.077) and (0.157, 0.107) and with maximum external quantum efficiencies (EQEmax) of 4.6% and 8.7%, respectively. It is the first time that the electroluminescence wavelength of TMCz based OLEDs reached below 450 nm with a CIEy below 0.11. Molecular engineering of the carbazole moiety is expected to provide a valuable strategy for molecular design of more deep blue emitters. [ABSTRACT FROM AUTHOR]

Two novel heteroleptic iridium complexes containing 4-phenylquinazoline (pqz) as a cyclometalating ligand, namely Ir1 and Ir2, are designed and synthesized. Methoxy groups are incorporated into the 6- and 7-sites of pqz rings to tune the physical properties and the emission performance of the complexes. The introduction of methoxy groups in Ir1 and Ir2 causes a slight blue shift by 3–5 nm relative to the reference complex Ir(pqz)2(acac) (630 nm), and moderate photoluminescence quantum yields of 0.35 and 0.38 and short lifetimes of 0.79 and 0.64 μs, respectively, are obtained. Ir1 and Ir2 are used as doped emitters to fabricate phosphorescence organic light-emitting diodes and pure red electroluminescence (EL) is achieved. In comparison with the reference complex Ir(pqz)2(acac), dramatically improved EL performance with color purity and efficiencies are realized for both Ir1 and Ir2. In particular, the Ir2 device exhibits a maximum external quantum efficiency of 26.22% with Commission Internationale de l'Eclairage (CIE) coordinates of (0.65, 0.34), which is close to the best efficiencies reported for other pqz based red iridium phosphors but advantageous in terms of a simple device structure with a single emitting layer. [ABSTRACT FROM AUTHOR]

It is strongly desired for thermally activated delayed fluorescence (TADF) compounds to possess a high rate constant of radiation (KR) and a high rate constant of reverse intersystem crossing (KRISC) simultaneously. A novel TADF compound, 3,6-di(10H-phenoxazin-10-yl)-10-phenylacridin-9(10H)-one (3,6-DPXZ-AD), is designed by attaching phenoxazine as the electron donor at the 3,6-sites of acridin-9(10H)-one as the acceptor. The unique sp2-hybridization of the nitrogen atom of the acridone ring leads to the quasi-equatorial conformation and the high molecular rigidity of 3,6-DPXZ-AD, which suppress conformation relaxation and finally generate a high KR of 1.4 × 107 s−1. The phosphorescence of 3,6-DPXZ-AD with unexpected higher energy than its fluorescence is proved to originate from the intermolecular through-space charge transfer state (TSCT) and the locally excited triplet states (3LE). Due to the multichannel RISC process from the TSCT and 3LE states to the 1CT state, a high KRISC of 1.1 × 106 s−1 is realized simultaneously. 3,6-DPXZ-AD shows a short TADF lifetime of 1.6 μs and a high fluorescence quantum yield of 94.9%. The yellow organic light-emitting diode with 3,6-DPXZ-AD as the doped emitter exhibits excellent performance with a low turn-on voltage of 2.2 V, an external quantum efficiency of 30.6% and a power efficiency of 109.9 lm W−1, being among the best values ever reported for acridone based materials. [ABSTRACT FROM AUTHOR]

Blue iridium phosphors are always precious and desirable for both fundamental research and industrial applications in organic light-emitting diodes (OLEDs). Three heteroleptic cyclometalated iridium(III) complexes, namely, Ir1, Ir2 and Ir3, incorporating 2-(3,5-bis(trifluoromethyl)phenyl)-pyrimidine (tfmphpm) or 2-(2,4-difluorophenyl)-pyrimidine (dfppm) as the main ligand, and 2-(3-(trifluoromethyl)-1H-pyrazol-5-yl)pyridine (fppz) or 2-(5-(4-(trifluoromethyl)phenyl)-2H-1,2,4-triazol-3-yl)pyridine (Htaz) as the ancillary ligand, were developed for application in OLEDs. Owing to the introduction of the strong-field CF3-containing ancillary ligand and the incorporation of electron-withdrawing F or CF3 groups on the HOMO-lying C-related aromatic rings of the C^N cyclometalating ligands, the phosphorescence of these Ir(III) complexes peaked at 457–459 nm. In comparison with the well-known commercial sky-blue iridium complex FIrpic (bis(4′,6′-difluorophenylpyridinato) iridium(III) picolinate, 475 nm), the phosphorescence of these complexes is hypsochromically shifted by 16–18 nm, more closely approaching standard blue light. They have high phosphorescence quantum yields in solution. The phosphorescent OLEDs employing these complexes as doped emitters display impressive performance. In particular, the PhOLED based on Ir3 achieves an outstanding maximum external quantum efficiency of 21.23% with Commission Internationale de l'Eclairage (CIE) coordinates of (0.15, 0.26), which is about 27% higher than that of the control device using FIrpic as a dopant (16.63%). [ABSTRACT FROM AUTHOR]