Synergism of molecular weight,crystallization and morphology of poly(3-butylthiophene) for photovoltaic applications

A serial of poly(3-butylthiophene) (P3BTs) with molecular weights (MWs) ranged from 7 kDa to 50 kDa is synthesized and characterized. The DSC studies show that the thermal property and crystallinity of P3BT increase with MWs within the range from 7 kDa to 25 kDa, then decrease with further higher MW. The characteristic morphologies of incontinuous crystalline nanofibrils, interconnected nanofibrillar networks, and relative large clusters associate to low, medium and high MW P3BTs, respectively, demonstrate the strong correlation between MW, crystallinity and morphology of P3BT. It is found that the P3BT could be re-considered as the promising candidate for applications in organic optoelectronics if synergism of the crystallinity and morphology could be precisely controlled via tuning molecular weight. The polymer solar cells (PSCs) device based on P3BT with medium MW achieves an attractive power conversion efficiency of 3.5%, which is, to the best of our knowledge, the record for P3BT/PC₆₁BM PSCs and comparable to the well-studied P3HT devices.     

Synthesis and Spectral and Structural Elucidation of Some Pyridinium Betaines of Squaric Acid: Potential Materials for Nonlinear Optical Applications

A series of substituted pyridinium betaines of squaric acid have been prepared by quaternization reaction of 3‐ and 4‐substituted pyridines with squaric acid. The products were characterized by means of elemental analysis, melting points, and their UV‐vis and IR spectra. The UV‐vis spectra of all investigated compounds in five different solvents were studied in detail. The UV‐vis spectral elucidation has given evidence of the clearly distinct negative solvatochromism of the pyridinium betaines of squaric acid, characteristic for compounds with a dipolar electronic ground state structure. The two absorption bands observed in the visible region show a charge‐transfer character, which determines their strong dependence on the polarity of the medium and the nature of the substituent. The investigation of the spectral behavior of pyridinium betaines of squaric acid has revealed their potential nonlinear optical and electro‐optical properties. Furthermore, these compounds exhibit remarkable thermal stability, required for such applications. The eventual technical application of these colored single crystals is discussed.     

场引晶体管双极理论:Ⅹ.基本物理和理论(所有器件结构)

本文描述半导体场引晶体管器件物理和理论所用的根本原则,它适用电场中有两种载流子的器件.讨论边界条件对器件电流电压特性的重要性.作为例子,计算两种边界条件下的转移直流电压特性:电势边界给出很高、流进内禀晶体管、飘移限制抛物型电流,电化学势边界仿真电子和空穴接触,给出很低、越过势垒注入、扩散限制电流,具有理想、每量级60mV、指数型亚阈值区倾斜.双MOS栅薄纯基硅场引晶体管为典型结构.     

场引晶体管双极理论:X.基本物理和理论（所有器件结构）

本文描述半导体场引晶体管器件物理和理论所用的根本原则,它适用电场中有两种载流子的器件.讨论边界条件对器件电流电压特性的重要性.作为例子,计算两种边界条件下的转移直流电压特性：电势边界给出很高、流进内禀晶体管、飘移限制抛物型电流,电化学势边界仿真电子和空穴接触,给出很低、越过势垒注入、扩散限制电流,具有理想、每量级60mV、指数型亚阈值区倾斜.双MOS栅薄纯基硅场引晶体管为典型结构.     

The dependence of the electrical and optical properties of molecular beam epitaxial Ino.52Alo.48As on growth parameters: Interplay of surface kinetics and thermodynamics

The optical and transport properties of In_0.52Al_o.48As grown by molecular beam epitaxy have been studied as a function of growth temperature in the range of 300-520° C. It is evident that under our growth conditions, thermodynamic considerations become important, and combined with surface kinetics, clustering effects become most severe for growth temperatures around 400° C. The clustering effects are manifested by changes in low-temperature photoluminescence, Hall transport and in the properties of Schottky diodes made on the films and the relevant parameters show a peaking for growth at 400° C. In particular, the Hall mobility exhibits a turning point forT > 300 K, beyond which the mobility increases with increasing temperature. In addition, the Hall electron concentration exhibits an anomalous reduction in value in the same high-temperature range. Measurements were also made on In_0.52Al_0.48As grown at 620-650° C by metalorganic chemical vapor deposition. While these films exhibit the same turning point in Hall mobility, the reduction in carrier concentration is significantly absent. Analysis of these data therefore indicates that the turning point in the mobility, which is present for both growth techniques, is caused by small clusters (~35Å) of phases slightly different from the mean composition. The reduction in electron concentration, seen only in the molecular beam epitaxial samples, suggest a more severe phase separation. A simple analysis for the sample grown at 400° C indicates that the compositions In_0.60Al_0.40As and In_0.44Al_0.56As might be present, in addition to the mean lattice-matched composition.