Role In Functional Devices Research Articles

Daytime passive radiative cooling materials based on disordered media: A review

Daytime passive radiative cooling (DPRC), a cooling method without extra energy consumption, has attracted more and more attentions in recent years. The strong reflection ability in the sunlight waveband (0.3–2.5 μm) and the intensive infrared radiative characteristic within the atmospheric window (8–13 μm), which called spectral selectivity, are the key point to realize DPRC. Spectral selectivity achieved by photonic crystals are difficult to promote on large scale because of complicated manufacturing process. With the rapid development of nanotechnology, materials with disordered media are playing an increasingly important role in functional devices. Combining disordered media with polymeric photonics will become an effective way to realize the large-scale preparation of DPRC materials. This review summarizes two kinds of disordered DPRC structures, paint and film with fillers, as well as porous polymers, including the influence of types, morphology, and particle size of fillers, as well as pore morphology, pore size distribution and preparation methods of porous polymers on the spectral performance and cooling effect of radiators. Also, we briefly introduce the biologically inspired microstructures for radiative cooling, in order to provide guidance for the practical application of DPRC materials.

Optically Controllable 2D Material/Complex Oxide Heterointerface.

Heterostructures play a vital role in functional devices on the basis of the individual constituents. Non‐conventional heterostructures formed by stacking 2D materials onto structurally distinct materials are of great interest in achieving novel phenomena that are both scientifically and technologically relevant. Here, a heterostructure based on a 2D (molybdenum ditelluride) MoTe2 and an amorphous strontium titanium oxide (a‐STO) thin film is reported. The heterostructure functions as a high‐performance photodetector, which exhibits anomalous negative photoresponse in the pristine device due to the scattering effect from the light‐induced Oδ‐ ions. The photoresponsivity and the specific detectivity are found to be >104 AW‐1 and >1013 Jones, respectively, which are significantly higher than those in standard MoTe2 devices. Moreover, through tuning the light programming time, the photodetection behavior of the MoTe2/a‐STO heterostructure experiences a dynamic evolution from negative to positive. This is due to the optically controllable modulation of the interfacial states, which is further confirmed by the X‐ray photoelectron spectroscopy and photoluminescence measurements. It is envisioned that the 2D material/a‐STO heterostructure could be a potential platform for exploring new functional devices.

Tailoring thermal conduction in anatase TiO2

Thermal conductivity (κ) plays an essential role in functional devices. It is advantageous to design materials where one can tune κ in a wide range according to its function: single-crystals and nanowires of anatase polymorph of titanium dioxide, broadly used in applications ranging from photovoltaics, reflective coatings to memristors, have been synthesized in large quantities. Here we identify a new, strong diffusion mechanism of heat by polaronic structures due to oxygen vacancies, which considerably influences both the absolute value and the temperature dependence of κ. The additional decrease of κ is achieved in anatase nanowires organized into foam, where porosity and the quasi-one-dimensional size-effect dramatically hinder the propagation of heat, resulting in an extremely low κ = 0.014 W/Km at room-temperature. Doping this anatase foam could herald promising applications, in particular in thermoelectricity.

On-Surface Route for Producing Planar Nanographenes with Azulene Moieties.

Large aromatic carbon nanostructures are cornerstone materials due to their increasingly active role in functional devices, but their synthesis in solution encounters size and shape limitations. New on-surface strategies facilitate the synthesis of large and insoluble planar systems with atomic-scale precision. While dehydrogenation is usually the chemical zipping reaction building up large aromatic carbon structures, mostly benzenoid structures are being produced. Here, we report on a new cyclodehydrogenation reaction transforming a sterically stressed precursor with conjoined cove regions into a planar carbon platform by incorporating azulene moieties in their interior. Submolecular resolution STM is used to characterize this exotic large polycyclic aromatic compound on Au(111) yielding unprecedented insight into a dehydrogenative intramolecular aryl-aryl coupling reaction. The resulting polycyclic aromatic carbon structure shows a [18]annulene core hosting peculiar pore states confined at the carbon cavity.