Optimization of CdTe thin‐film solar cell efficiency using a sputtered,oxygenated CdS window layer

A major source of loss in cadmium sulfide/cadmium telluride (CdS/CdTe) solar cells results from light absorbed in the CdS window layer, which is not converted to electrical current. This film can be made more transparent by oxygen incorporation during sputter deposition at ambient temperature. Prior to this work, this material has not produced high‐efficiency devices on tin oxide‐coated soda‐lime‐glass substrates used industrially. Numerous devices were fabricated over a variety of process conditions to produce an optimized device. Although the material does not show a consistent increase in band gap with oxygenation, absorption in this layer can be virtually eliminated over the relevant spectrum, leading to an increase in short‐circuit current. Meanwhile, fill factor is maintained, and open‐circuit voltage increases relative to baseline devices with sublimated CdS. The trend of device parameters with oxygenation and thickness is consistent with an increasing conduction band offset at the window/CdTe interface. Optimization considering both initial efficiency and stability resulted in a National Renewable Energy Laboratory verified 15.2%‐efficient cell on 3.2‐mm soda‐lime glass. This window material was shown to be compatible with SnO₂‐based transparent conducting oxide and high resistance transparent coated substrates using in‐line compatible processes. Copyright © 2015 John Wiley & Sons, Ltd     

The effect of compatibilization on the behavior of a polycarbonate/polymer liquid crystal blend

Polymer liquid crystalline materials (PLC) blended with engineering plastics (EP) have the potential to reduce viscosity and increase the modulus of the EP, particularly if the PLC is in a favorable fibrillar morphology. A major deficiency in these blends—as with many other immiscible polymeric systems—is poor failure properties. In this paper, polycarbonate (PC) and a rigid, all-aromatic commercial PLC are blended and a third resin, a copolymer of methyl methacrylate and N-methyl-dimethyl-glutarimide is included as a compatibilizing agent. Characterization of the binary and ternary blends is carried out using rheological, mechanical, morphological, and dynamic mechanical characterization techniques. Binary blends of PLC in a PC matrix result in an immiscible, nodular morphology with low failure stresses. The addition of the copolymeric compatibilizer—particularly one with reactive functionalities—is found to improve tensile strength and yield a fibrillar blend morphology. It is proposed that this may be due to the compatibilizer reducing interfacial tension and adhering to the blend phases, rather than by causing a major change in blend viscosity.     

新型高效而紧凑的白光LED驱动方案

系统设计人员目前面临一个艰巨的挑战,他们需要利用彩色便携式显示屏来最大限度地提升系统功能和效率,同时又要实现成本和尺寸最小化.现在已经到了需要为系统设计师提供一种全新的LED驱动拓扑的时候.     

Impact Sensitivity Reduction Via Exo-Electron Control

Many materials, upon fracturing, emit electrons (exo-electrons) by a process called fracto-emission. For a substance or mixture that can deflagrate or detonate upon impact or friction, these exo-electrons may contribute to the initiation of deflagration or detonation. Some materials, such as p-type semiconductors, can absorb exo-electrons and, as used as additives, can reduce the impact or friction sensitivity of propellants or explosives. It was found that the addition of 1% p-type silicon powder did decrease the impact sensitivity of a propellant consisting of ammonium perchlorate in a polybutadiene matrix, but did not reduce the impact sensitivity of powdered cyclotetramethylenetetranitramine (HMX), cyclotrimethylenetrinitramine (RDX), and pentaerythritol trinitrate (PETN).     

Gas chromatographic-olfactometric characterization of aroma active compounds in sun-dried and vacuum-dried tarhana

The influence of drying methods on the aroma active volatiles of sun-dried tarhana (SDT) and vacuum-dried tarhana (VDT) were compared using headspace SPME, GC-O and GC-MS. Although vacuum drying reduced the total amount of volatiles as compared to SDT (total FID peak area), more aroma active material was retained with VDT (total olfactory peak area). Vacuum drying retained a greater number of aroma active components (41) whereas the sun-dried method retained only 23. Aldehydes were the largest single class of aroma compounds in both types of tarhana: 17 in VDT and 10 in SDT. Other differentiating aroma compounds include alcohols, terpenes, and phenols such as geraniol, terpinolene, and 4-vinylguaiacol among others. A total of 22 aroma active components were present in greater amounts in the VDT versus only four aroma compounds present in greater amounts in the SDT.     

Preparation and properties of stereoregular poly(hydroxyethyl methacrylate) polymers and hydrogels

Linear poly(hydroxyethyl methacrylate) (PHEMA) has been synthesized in highly syndiotactic and highly isotactic configurations. The high syndiotactic PHEMA prepared by u.v. photolysis at ?40° C was found by ¹³C n.m.r. to have a tactic triad content of 84% syndio, 16% hetero and 0% iso. High isotactic PHEMA was prepared by anionic polymerization of benzoxyethyl methacrylate in toluene followed by selective hydrolysis of the benzoate ester, and was observed by ¹³C n.m.r. to have a 5% syndio, 15% hetero and 80% isotactic triad content. A linear PHEMA polymer formed by radical polymerization at 60°C in ethanol solvent was found to have a tactic triad content of 58% syndio, 42% hetero and 0% iso. These polymers have been crosslinked with hexamethylene diisocyanate and their water swelling properties determined as functions of temperature and crosslinker concentration. Isotactic PHEMA exhibited greater aqueous swelling below 30° C than the syndiotactic PHEMA samples. The stereochemistry of the polymer chain is shown to be a factor in determining the swelling behaviour of hydrophilic methacrylate gels.