Inorganic Electron Transport Materials in Perovskite Solar Cells

In the past decade, the perovskite solar cell (PSC) has attracted tremendous attention thanks to the substantial efforts in improving the power conversion efficiency from 3.8% to 25.5% for single-junction devices and even perovskite-silicon tandems have reached 29.15%. This is a result of improvement in composition, solvent, interface, and dimensionality engineering. Furthermore, the long-term stability of PSCs has also been significantly improved. Such rapid developments have made PSCs a competitive candidate for next-generation photovoltaics. The electron transport layer (ETL) is one of the most important functional layers in PSCs, due to its crucial role in contributing to the overall performance of devices. This review provides an up-to-date summary of the developments in inorganic electron transport materials (ETMs) for PSCs. The three most prevalent inorganic ETMs (TiO₂, SnO_2, and ZnO) are examined with a focus on the effects of synthesis and preparation methods, as well as an introduction to their application in tandem devices. The emerging trends in inorganic ETMs used for PSC research are also reviewed. Finally, strategies to optimize the performance of ETL in PSCs, effects the ETL has on J–V hysteresis phenomenon and long-term stability with an outlook on current challenges and further development are discussed.     

Magnetic effects of direct ion implantation of Mn and Fe into p-GaN

In p-GaN implanted with Mn (3×10¹⁶ cm⁻² at 250 keV), the material after annealing shows ferromagnetic properties below 250 K. Cross-sectional transmission electron microscopy (TEM) revealed the presence of platelet structures with hexagonal symmetry. These regions are most likely Ga_xMn_1−xN, which produce the ferromagnetic contribution to the magnetization. In p-GaN implanted with Fe, the material after annealing showed ferromagnetic properties at temperatures that were dependent on the Fe dose, but were below 200 K in all cases. In these samples, TEM and diffraction analysis did not reveal any secondary phase formation. The results for the Fe implantation are similar to those reported for Fe doping during epitaxial growth of GaN.     

Magnetism in SiC implanted with high doses of Fe and Mn

High concentrations (0.1–5 at.%) of Mn or Fe were introduced into the near-surface region (≤2000 Å) of 6H-SiC substrates by direct implantation at ～300°C. After annealing at temperatures up to 1000°C, the structural properties were examined by transmission electron microscopy (TEM) and selected-area diffraction pattern (SADP) analysis. The magnetic properties were examined by SQUID magnetometry. While the Mn-implanted samples were paramagnetic over the entire dose range investigated, the Fe-implanted material displayed a ferromagnetic contribution present at <175 K for the highest dose conditions. No secondary phases were detected, at least not to the sensitivity of TEM or SADP.     

Raptor electrocutions

Distribution power line raptor electrocutions have been studied extensively since 1971. Numerous methods to modify power line structures to eliminate the potential for electrocutions have been developed, published, and utilized by the electric utility industry. Some of the modified overhead distribution line construction units have been adopted as standards by investor owned utilities and the Rural Utilities Service, dramatically reducing raptor electrocutions. Although utility construction practices have improved greatly since 1971, some raptor electrocutions still persist. Many utilities today are employing larger crossarms in their new construction to provide increased phase-to-phase and phase-to-ground separation to reduce the potential for electrocutions. Although an emphasis on providing increased phase separation may eliminate some electrocutions, uninsulated jumper wires may pose a greater threat to raptors. A review of utility raptor electrocution forms filed since 1985 indicates that overhead distribution power line poles configured with transformers and bare jumpers are associated with the most raptor electrocutions. Pole configurations and mitigation of raptor electrocutions are discussed     

Detection for a statistically known, time-varying dispersivechannel

Detection for the statistically known channel (SKC) is aimed at obtaining good performance in situations where our statistical knowledge of a time-varying channel is good, and where other equalization/detection schemes are either too complex to implement, or their performance is limited due to the rapidity of channel fading, or where we are simply unable to perform channel estimation. By using a statistical characterization of the channel, we develop a new detector that performs maximum-likelihood sequence estimation (MLSE) (given the channel model) on blocks of N symbols. Both symbol-spaced and fractionally spaced samples are used, to obtain two different detectors, that are generalizations of those devised for optimal block schemes on nondispersive channels. The detector that uses fractionally spaced samples is shown to outperform the detector that uses symbol-spaced samples. The performance of both appears to approach that of the corresponding known channel (KC) detector as the block length increases. We also numerically evaluate the SKC detector performance under conditions where the channel parameters (statistics) are incorrectly estimated, and show that the fractionally spaced detector is fairly robust to modeling errors. Finally, we devise a sliding block algorithm, for use when transmitting more than N symbols     

Optimisation of enhancement layer DCT coefficients in MPEG-2 SNRscalable video

The authors describe an optimisation algorithm which can be applied to two-layer SNR scalable MPEG-2 video coding, such that bandwidth efficiency is achieved which is comparable to single-layer coding. Our optimised two-layer coder is shown to generate as little as 1% fewer bits than a single-layer coder compared to up to 15% more bits generated by the non-optimised SNR scalable coder     

Quantum interference effects in semiconductors: a bibliography

The bibliography has been compiled as an introduction and study guide to this field. The papers listed describe the extensive theoretical and experimental results that have been obtained on quantum interference effects and discuss possible application areas. Works of a fundamental nature concerning phenomena that are basic to all semiconductor behavior have not been included. Articles on the properties and band structure of semiconductors, which are essential to a complete understanding of quantum interference effects, have not been included. Conference papers, though frequently very important, have not been included to conserve space. The papers are listed alphabetically according to the first author's surname. As in the compilation of any bibliography, numerous valuable and pertinent articles have probably been inadvertently omitted     

Physical design issues for very large ATM switching systems

The authors examine the physical design issues associated with terabit/second switching systems, particularly with regard to the customer access portion of the switch. They determine the physical design requirements in the areas of backplane interconnections, integrated circuit packaging, and circuit board technology and identify areas where existing- or near-future physical design technologies are inadequate to meet the requirements of this application. A new 3D interconnection architecture that solves some of the problems encountered at the backplane level is suggested. It is also suggested that multichip module technology will help meet some of the speed and density requirements at the chip packaging level. Some of the system-level consequences of the proposed model are discussed     

Crystallinity in PPS–carbon composites: A study using diffuse reflection FT-IR spectroscopy and differential scanning calorimetry

A method based on diffuse reflection Fourier transform infrared (FT-IR) spectroscopy has been developed for determining the state of crystallinity in composite materials made from poly(phenylene sulfide) (PPS) reinforced with carbon fibers. Using this technique, good-quality spectra can be obtained directly from the surface of prepreg or molded composite; thus the method is rapid and nondestructive. Several peaks in the spectrum are sensitive to the crystallinity and can be used for quantitative characterization purposes. The recommended indicator is the ratio of the heights of the peaks at 1075 and 1093 cm^?1. Using a range of samples of varying crystallinity prepared by annealing amorphous prepreg, it has been shown that there is a very good correlation between this ratio and the enthalpy of crystallization as determined by differential scanning calorimetry. The effects of such annealing, as well as heating in air at high temperatures, have been investigated.     

Efficiency of plasticization of PVC by higher-order di-alkyl phthalates and survey of mathematical models for prediction of polymer/diluent blend Tg's

Presently, a suitable theory to predict the T_g vs. composition relationship for a given polymer-plasticizer blend, based on detailed molecular structure and molecular energitics considerations, is not available. In particular, the plasticizer efficiency parameter, k, which is uniquely defined at low-to-moderate diluent concentrations, and is an essential variable in the Mauritz-Storey theory of the diffusion of large molecules in amorphous polymers in the rubbery state, must always be determined by experiment. In this work, k was determined by DSC for PVC that was plasticized over a range of concentrations with a number of higher branched and linear di-alkyl phthalates. The results will be used in our plasticizer diffusion theory as well as provide guidance in the future development of a general mathematical model for predicting k. It was seen that k decreased with increasing molecular weight for both the linear and branched phthalates. For a given molecular weight, the branched phthalates have higher k values than the linear structures. These results have been rationalized in terms of the additional free volume created by the inefficiency of packing polymer chains about these large penetrant molecules. The DSC scans also implied an increasing degree of microstructural heterogeneity with increasing plasticizer concentration. Finally, relationships between plasticizer diffusion coefficient in the rubbery state and the plasticized T_g were established for low-to-moderate diluent concentration for three of the plasticizers studied by utilizing experimental diffusion data from our earlier work on these systems.