RESUMEN
All-day passive radiative cooling has recently attracted broader attention for its potential as a viable energy technology. Although tremendous progress has been achieved, the design and fabrication of low-cost high-efficiency radiators for all-day passive radiative cooling remains a challenge. Herein, we report a new type of flexible composite radiator film with built-in artificial opal-like structures for all-day passive radiative cooling. Using artificial opal structure concepts, the proposed polydimethylsiloxane (PDMS) radiator film with embedded polystyrene (PS) microsphere photonic crystals exhibits a sufficiently high solar reflectance of â¼92.7% when in a direct sunlight region, and a thermal emittance of â¼93.6% within the atmospheric window. Without the need for traditional reflectors like silver or aluminum foils, this composite film realizes subambient temperature reduction of â¼4.8 °C in direct sunlight and â¼8.5 °C during the night. This work provides a new fabrication approach for the low-cost production of structural polymer films for high performance and potential real word applications.
RESUMEN
Although there have been tremendous achievements ever since the first work on an organic electroluminescent (EL) device that emitted polarized light, the development of flexible polarized emission organic light-emitting devices (OLEDs) is not without hurdles, and the challenge towards real-world applications still requires tremendous effort. In this paper, we proposed highly linearly polarized light-emission from flexible green OLEDs capitalized on integrated ultrathin metal-dielectric nanograting. The acquired polarized device with meticulously optimized geometric parameters yields an angle-invariant average extinction ratio beyond 20.0 dB within a viewing angle range of ± 60°. The detailed analysis illustrates that surface plasmons and cavity modes are simultaneously contributed to the TM-polarized light selection. We hope that the presented approach will open new opportunities for designing flexible polarized light sources.
RESUMEN
A new approach for efficiently recovering the wasted light energy in conventional flexible organic light-emitting diodes (FOLEDs) is developed by implementing disordered micro-meander structures (DMMs) via laser speckle holography technology. Compared to conventional flat device architecture, the structured FOLEDs with DMMs result in substantial improvement of the device efficiency and superior angular color stability. The resulting current efficiency (CE) and external quantum efficiency (EQE) are 1.31 and 1.39 times that of a common flat structure, respectively. Moreover, the proposed DMMs micro-structure simultaneously offers the unique characteristics of angular color stability with a wide viewing angle, which is usually considered as the criteria of the high-quality lighting applications. We hope that the demonstrated method could provide an alternative way for the development of high efficiency flexible OLEDs.
RESUMEN
Two novel D-A bipolar blue phosphorescent host materials based on phenothiazine-5,5-dioxide: 3-(9H-carbazol-9-yl)-10-ethyl-10H-phenothiazine-5,5-dioxide (CEPDO) and 10-butyl-3-(9H-carbazol-9-yl)-10H-phenothiazine-5,5-dioxide (CBPDO) were synthesized and characterized. The photophysical, electrochemical and thermal properties were systematically investigated. CEPDO and CBPDO not only have a high triplet energy but also show a bipolar behavior. Moreover, their fluorescence emission peaks are in the blue fluorescence region at 408 nm and the fluorescence quantum efficiency (Φ) of CEPDO and CBPDO were 62.5% and 59.7%, respectively. Both CEPDO and CBPDO showed very high thermal stability with decomposition temperatures (Td) of 409 and 396 °C as well as suitable HOMO and LUMO energy levels. This preferable performance suggests that CEPDO and CBPDO are alternative bipolar host materials for the PhOLEDs.
RESUMEN
Mechanisms of charge transport between the interconnector and its neighboring layers in tandem organic photovoltaic cells have been systematically investigated by studying electronic properties of the involving interfaces with photoelectron spectroscopies and performance of the corresponding devices. The results show that charge recombination occurs at HATCN and its neighboring hole transport layers which can be deposited at low temperature. The hole transport layer plays an equal role to the interconnector itself. These insights provide guidance for the identification of new materials and the device architecture for high performance devices.
RESUMEN
A simply and facilely synthesized MoO3 solution was developed to fabricate charge injection layers for improving the charge-injection properties in p-type organic field-effect transistors (OFETs). By dissolving MoO3 powder in ammonium (NH3) solvent under an air atmosphere, an intermediate ammonium molybdate ((NH4)2MoO4) precursor is made stable, transparent and spin-coated to form the MoO3 interfacial layers, the thickness and morphology of which can be well-controlled. When the MoO3 layer was applied to OFETs with a cost-effective molybdenum (Mo) electrode, the field-effect mobility (µFET) was significantly improved to 0.17 or 1.85 cm(2) V(-1)s(-1) for polymer semiconductors, regioregular poly(3-hexylthiophene) (P3HT) or 3,6-bis-(5bromo-thiophen-2-yl)-N,N'-bis(2-octyl-1-dodecyl)-1,4-dioxo-pyrrolo[3,4-c]pyrrole (DPPT-TT), respectively. Device analysis indicates that the MoO3-deposited Mo contact exhibits a contact resistance RC of 1.2 MΩ cm comparable to that in a device with the noble Au electrode. Kelvin-probe measurements show that the work function of the Mo electrode did not exhibit a dependence on the thickness of MoO3 film. Instead, ultraviolet photoemission spectroscopy results show that a doping effect is probably induced by casting the MoO3 layer on the P3HT semiconductor, which leads to the improved hole injection.