Multilayer indium-tin-oxide (ITO)–Ag–ITO stacks were evaluated as transparent conductors for flexible organic light-emitting diode (OLED) displays. The ITO–metal–ITO (IMI) samples exhibited significantly reduced sheet resistance over ITO and greater than 80% optical transmission. The IMI films deposited on plastic substrates showed dramatically improved mechanical properties when subjected to bending both as a function of radius of curvature as well as number of cycles to a fixed radius. OLEDs were fabricated on both ITO and IMI anodes, and the devices with IMI anodes showed improved performance at current densities greater than 1mA∕cm2 due to the improved conductivity of the anode.
In present-day high-performance electronic components, the generated heat loads result in unacceptably high junction temperatures and reduced component lifetimes. Thermoelectric modules can, in principle, enhance heat removal and reduce the temperatures of such electronic devices. However, state-of-the-art bulk thermoelectric modules have a maximum cooling flux qmax of only about 10 W cm−2, while state-of-the art commercial thin-film modules have a qmax <100 W cm−2. Such flux values are insufficient for thermal management of modern high-power devices. Here we show that cooling fluxes of 258 W cm−2 can be achieved in thin-film Bi2Te3-based superlattice thermoelectric modules. These devices utilize a p-type Sb2Te3/Bi2Te3 superlattice and n-type δ-doped Bi2Te3−xSex, both of which are grown heteroepitaxially using metalorganic chemical vapour deposition. We anticipate that the demonstration of these high-cooling-flux modules will have far-reaching impacts in diverse applications, such as advanced computer processors, radio-frequency power devices, quantum cascade lasers and DNA micro-arrays.
Clean renewable energy sources (e.g., solar, wind, and hydro) offers the most promising solution to energy and environmental sustainability. On the other hand, owing to the spatial and temporal variations of renewable energy sources, and transportation and mobility needs, high density energy storage and efficient energy distribution to points of use is also critical. Moreover, it is challenging to scale up those processes in a cost-effective way. Electrochemical processes, including photoelectrochemical devices, batteries, fuel cells, super capacitors, and others, have shown promise for addressing many of the abovementioned challenges. Materials with designer properties, especially the interfacial properties, play critical role for the performance of those devices. Atomic layer deposition is capable of precise engineering material properties on atomic scale. In this review, we focus on the current state of knowledge of the applications, perspective and challenges of atomic layer deposition process on the electrochemical energy generation and storage devices and processes.
RTI has developed a photodiode technology based on solution-processed PbS colloidal quantum dots (CQD). These devices are capable of providing low-cost, high performance detection across the Vis-SWIR spectral range. At the core of this technology is a heterojunction diode structure fabricated using techniques well suited to wafer-scale fabrication, such as spin coating and thermal evaporation. This enables RTI's CQD diodes to be processed at room temperature directly on top of read-out integrated circuits (ROIC), without the need for the hybridization step required by traditional SWIR detectors. Additionally, the CQD diodes can be fabricated on ROICs designed for other detector material systems, effectively allowing rapid prototype demonstrations of CQD focal plane arrays at low cost and on a wide range of pixel pitches and array sizes. BACKGROUNDSemiconductor particles with radii less than 10 nm -often referred to as colloidal quantum dots (CQD) or semiconductor nanocrystals-have been the focus of considerable research in the past fifteen years. Owing to the effects of quantum confinement CQDs have optical and electronic properties that are size dependent and can be tuned during synthesis to span a broad range of energies.[1] The lowest energy transition for a quantum dot defines the effective bandgap and is referred to as the first excitonic transition. An illustration contrasting the bandgap of bulk PbS with the first and second excitonic transition of quantum confined PbS can be seen in Figure 1.Because the bandgap of a nanocrystal begins with that of the bulk material and subsequently shifts up in energy, certain semiconductors are more suitable to specific applications than others. PbS, for example, has a bulk bandgap of 0.41 eV (3100 nm) and PbS CQDs can be tuned to have bandgaps across the spectral region of 700-2400 nm. This makes them suitable for Vis-SWIR emitters, detectors, modulators, and photovoltaics [2][3][4][5][6]. Moreover, these materials continue to absorb through UV and even x-ray energies.CQDs are synthesized in solution through straightforward chemical techniques and are then subsequently processed from solution to form thin films for use in electronic devices. Figure 1 shows a vial of PbS CQDs in solution and an image of CQDs being spray coated onto a substrate. The simplicity of device fabrication, which requires only processes such as spin coating and thermal evaporation and the low cost of device materials means that components fabricated using CQDs are expected to be extremely low cost and scalable to high volume manufacturing.
Graphene has amazing abilities due to its unique band structure characteristics defining its enhanced electrical capabilities for a material with the highest characteristic mobility known to exist at room temperature. The high mobility of graphene occurs due to electron delocalization and weak electron-phonon interaction, making graphene an ideal material for electrical applications requiring high mobility and fast response times. In this review, we cover graphene's integration into infrared IR devices, electro-optic EO devices, and field effect transistors FETs for radio frequency RF applications. The benefits of utilizing graphene for each case are discussed, along with examples showing the current state-of-the-art solutions for these applications.Graphene has many outstanding properties due to its unique bonding and subsequently band gap characteristics, having electronic carriers act as massless DiracFermions. The material characteristics of graphene are anisotropic, having phenomenal characteristic within a single sheet and diminished material characteristics between sheet with increasing sheet number and grain boundaries. We will discuss the integration of graphene into many electronic device applications.Graphene has the highest mobility values measured in a material at room temperature, allowing integration into fast response time devices such as a high electron mobility transistor HEMT for RF applications. Graphene has shown promise in IR detectors by utilizing graphene in thermal-based detection applications.
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