Organisch–anorganische Heterostrukturen spielen eine zentrale Rolle in modernen elektronischen und optoelektronischen Anwendungen. Dazu gehören Photodetektoren und Feldeffekttransistoren sowie die ...Umwandlung von Solarenergie mithilfe von Photoelektroden für Farbstoffsolarzellen, photoelektrochemischen Zellen und organischen Photovoltaiksystemen. Die Leistung solcher Systeme wird zu großen Teilen durch die Dynamik des Ladungstransfers an und zwischen (inneren) Grenzflächen, z. B. zwischen einem Halbleiter mit großer Bandlücke und molekularen Sensibilisatoren und/oder Katalysatoren, bestimmt. Daher ist ein detailliertes Verständnis der Beziehung zwischen Struktur, Dynamik und Funktion solcher funktionalen Grenzflächen notwendig, um mögliche Limitationen der Leistungsfähigkeit dieser Materialien und Systeme auf molekularer Ebene zu erklären. Die Summenfrequenzspektroskopie (SFS) als grenzflächenempfindliche Technik ermöglicht es, spezifische chemische Informationen über Grenzflächen zu erhalten. Wird diese in ein Anregungs‐Abfrage‐Schema integriert, liefert sie neben solchen chemischen Erkenntnissen eine ultraschnelle Zeitauflösung. Dieser Mini‐Review‐Artikel diskutiert die Vorteile und das Potenzial der SFS für die Untersuchung von Ladungstransferdynamiken an Grenzflächen und von strukturellen Veränderungen an inneren Grenzflächen. Es wird ein wichtiger Beitrag dieser einzigartigen spektroskopischen Einblicke in ansonsten unzugängliche Grenzflächen vorgestellt, der, so hoffen wir, neue Wege für ein besseres Verständnis der funktionsbestimmenden Prozesse in komplexen Materialien aufzeigt. Damit sollen Gemeinschaften, die sich dem Design von Materialien und Bauteilen widmen, mit Spektroskopikern zusammengebracht werden.
Die komplizierten Strukturen anorganisch–organischer hybrider Heterostrukturen, die in der organischen Photovoltaik, in Farbstoffsolarzellen und der organischen Optoelektronik verwendet werden, erfordern eine eingehende Untersuchung ihrer funktionellen Grenzflächen. Dieser Mini‐Review‐Artikel bietet einen Ausblick auf die Anwendung der (zeitaufgelösten) Summenfrequenzspektroskopie ((TR‐)SFS) zur Erforschung der Ladungsdynamik und ihres Einflusses auf die Grenzflächenstruktur dieser Bauteile.
Display omitted
•Gas-sensing CeO2–SnO2 heterostructures were prepared using hydrothermal approach.•CeO2-SnO2 showed higher surface area and defects related to VO.•CeO2-SnO2 displayed higher ...selectivity to H2 gas at 300°C.•CeO2-SnO2 revealed higher sensitivity of 19.23ppm−1 to 40ppm H2 gas at 300°C.
Detection of toxic and explosive gases in a selective manner and with higher sensitivity in industries and homes remains very challenging. Therefore, herein, we report on the ultra-high sensitive and selective hydrogen gas sensing using CeO2-SnO2 mixed oxide heterostructure synthesized by a simple hydrothermal method. The BET, photoluminescence, X-ray photoelectron spectroscopy and electron paramagnetic resonance analyses demonstrated that the CeO2-SnO2 heterostructure comprehends a high surface area and a large number of defects related to oxygen vacancies. The formation of heterojunction in CeO2-SnO2 nanostructures was confirmed by the non-linear behaviour I–V curve. The gas-sensing characteristics of the CeO2-SnO2 heterostructure showed shorter response and recovery times of approximately 17 and 24s, respectively, together with high sensitivity (19.23ppm−1) to 40.00ppm H2 gas at 300°C. The improved H2 gas sensing response of 1323 at 60ppm H2 gas is correlated with the higher surface area, pore diameter, surface defects and CeO2-SnO2 heterojunction emerging at the interfaces between the CeO2 and SnO2 serves as additional reaction sites and as well as exposed facets creating the surface to be extremely reactive for the adsorption of oxygen species. The high H2 gas selectivity observed for the CeO2-SnO2 makes them possible candidates for monitoring H2 gas at low concentrations (ppm levels).
Display omitted
•Porous CuO/ZnO heterostructural tube was simply fabricated by using absorbent cotton.•The response/recovery time is the fastest in present ZnO-based ppb-level H2S sensors.•The sensor ...shows excellent selectivity, good repeatability and long-term stability.
The development of ZnO-based sensors towards the detection of trace H2S has recently aroused extensive attentions due to its very harmful to human health even at a concentration as low as 83 ppb. However, the fast response/recovery ZnO-based sensors for detecting ppb-level H2S were also challenging. In this study, porous CuO/ZnO heterostructural tubule was facilely and massively prepared by metal salt impregnation and subsequently calcination via confined effect of absorbent cotton. The influence of Cu2+ doping amounts and calcination temperature on the corresponding microstructure and gas sensing properties of the composites is investigated. The precursor with 3.67 at% Cu2+ doping was calcined at 600 °C to form heterostructural tubules (3.67 at% CuO/ZnO-600) with the specific surface area of 35.2 m2 g−1, which consist of monoclinic CuO (˜21.8 nm) and hexagonal ZnO (˜33.7 nm). The sensor based on 3.67 at% CuO/ZnO-600 shows better gas sensitivity to 50 ppb H2S at 170 °C with response and recovery times of 35 and 29 s, which represents the fastest response/recovery properties in reported ZnO-based ppb-level H2S sensors to date. Furthermore, the sensor has a low detection limit of 10 ppb and shows a wide linear range from 10 to 1000 ppb, good repeatability and long-term stability. Such excellent ppb-level H2S gas sensing performance is mainly ascribed to the inherent characteristics of hierarchically porous tubular structure, p-n heterojunction and surface adsorbed oxygen species. Moreover, the gas-sensing mechanism is also investigated in detail.
The rediscovery of graphene in 2004 triggered an explosive expansion of research on various van der Waals (vdW) materials. The atomic layers of these vdW materials do not have surface crystal defects ...and are bonded by weak vdW interactions, thus the vdW materials can be stacked onto each other to form vdW heterojunction structures without needing to consider the lattice mismatch issue. In addition, the broad library of vdW materials makes it possible to design diverse types of heterojunctions with a wide range of band alignments, bandgaps, and electron affinities. Vertical vdW heterostructures especially offer numerous possibilities for the realization of high-performance electronic and optoelectronic devices. Therefore, these vdW heterostructures have received significant attention, and extensive relevant experimental results have been reported in the past few years. In this review, we first introduce the transfer techniques to form vdW heterojunction structures. Next, we discuss recent progress in vdW heterostructure-based electronic and optoelectronic devices, including vertical field effect transistors, negative differential resistance devices, memories, photodetectors, photovoltaic devices, and light-emitting diodes. Finally, we conclude this review by discussing the current challenges facing vdW heterojunction structure-based devices and our perspective on future research directions.
Display omitted
We provide the first NREL‐certified efficiency measurement on an all‐inorganic, solution‐processed, nanocrystal solar cell. The 3% efficient device is composed of ZnO nanocrystals and 1.3 eV PbS ...quantum dots with gold as the top contact. This configuration yields a stable device, retaining 95% of the starting efficiency after a 1000‐hour light soak in air without encapsulation.
We consider the role of deformations in graphene heterostructures with hexagonal crystals (including strain, wrinkles and dislocations) on the geometrical properties of moiré patterns characteristic ...for a pair of two incommensurate misaligned isostructural crystals. By employing a phenomenological theory to describe generic moiré perturbations in van der Waals heterostructures of graphene and hexagonal crystals we investigate the electronic properties of such heterostructures.
PDF
