有机光伏异质结氟化苯三唑聚合物给体/十环熔合非富勒烯受体的理论研究

本文为了理解由十环熔合非富勒烯受体和含有氟化苯三唑聚合物给体组成的有机光伏器件的优异光伏性能(光电转换效率大于13%),借助深入的量子化学计算,研究了氟化苯三唑聚合物给体、十环熔合非富勒烯受体及其异质结界面模型面-面相向构型复合物的几何结构、分子轨道、激发特性、分子表面静电势、转移电量和电荷转移距离.结果表明,氟化苯三唑聚合物给体:十环熔合非富勒烯受体异质结的卓越光伏性能是由于十环熔合非富勒烯受体分子内给体和受体片段之间的共面性,氟化苯三唑聚合物给体和十环熔合非富勒烯受体的电荷转移和杂化激发,在可见区域的互补光学吸收,以及从氟化苯三唑聚合物给体到十环熔合非富勒烯受体的分子表面静电势差值较大引起的.氟化苯三唑聚合物给体/十环熔合非富勒烯受体复合物的电子结构和激发表明,激子解离可以通过基于空穴转移的受体局域激发的衰退来实现,这不同于基于富勒烯受体的有机光伏的激子解离机理.通过Marcus理论评估的激子解离、电荷复合和电荷转移过程的速率常数表明有效的激子解离也是良好光伏性能的原因.

Age and geochemistry of the granitoid from the Lunte area,Northeastern Zambia:Implications for magmatism of the Columbia supercontinent

The Paleoproterozoic tectonic evolution of the Bangweulu Block has long been controversial.Paleoproterozoic granites consisting of the basement complex of the Bangweulu Block are widely exposed in northeastern Zambia,and they are the critical media for studying the tectonic evolution of the Bangweulu Block.This study systematically investigated the petrography,zircon U-Pb chronology,and petrogeochemistry of the granitoid extensively exposed in the Lunte area,northeastern Zambia.The results show that the granitoid in the area formed during 2051±13-2009±20 Ma as a result of Paleoproterozoic magmatic events.Geochemical data show that the granites in the area mainly include syenogranites and monzogranites of high-K calc-alkaline series and are characterized by high SiO2 content(72.68%‒73.78%)and K_(2)O/Na_(2)O ratio(1.82‒2.29).The presence of garnets,the high aluminum saturation index(A/CNK is 1.13‒1.21),and the 1.27%‒1.95%of corundum molecules jointly indicate that granites in the Lunte area are S-type granites.Rare earth elements in all samples show a rightward inclination and noticeably negative Eu-anomalies(δEu=0.16‒0.40)and are relatively rich in light rare earth elements.Furthermore,the granites are rich in large ion lithophile elements such as Rb,Th,U,and K and are depleted in Ba,Sr,and high field strength elements such as Ta and Nb.In addition,they bear low contents of Cr(6.31×10^(−6)‒10.8×10^(−6)),Ni(2.87×10^(−6)‒4.76×10^(−6)),and Co(2.62×10^(−6)‒3.96×10^(−6)).These data lead to the conclusion that the source rocks are meta-sedimentary rocks.Combining the above results and the study of regional tectonic evolution,the authors suggest that granitoid in the Lunte area were formed in a tectonic environment corresponding to the collision between the Tanzania Craton and the Bangweulu Block.The magmatic activities in this period may be related to the assembly of the Columbia supercontinent.

Simulation of Melting Behavior of the MgSi03 Perovskite Under Lower Mantle Conditions

The melting curve of MgSiO3 perovskite was simulated using molecular dynamics method combining with the effective pair potentials under the lower mantle conditions. It was shown that the state equation simulated for MgSiO3 perovskite is very successful in reproducing accurately the experimental data over a wide range of pressure. The pressure dependence of the simulated melting temperature of MgSiO3 perovskite is in agreement with the recent experimental data. The melting curve simulated for MgSiO3 is very steep at pressures below 60 GPa first, then it becomes smooth with increasing pressure. At the core mantle boundary pressure 135 GPa, MgSiO3 perovskite melts at 6500 K, which is significantly lower than that of the extrapolations of the experimental data from Zerr and Boehler.

First-principles study of stability of point defects and their effects on electronic properties of GaAs/AlGaAs superlattice

When the GaAs/AlGaAs superlattice-based devices are used under irradiation environments, point defects may be created and ultimately deteriorate their electronic and transport properties. Thus, understanding the properties of point defects like vacancies and interstitials is essential for the successful application of semiconductor materials. In the present study, first-principles calculations are carried out to explore the stability of point defects in GaAs/Al_(0.5)Ga_(0.5)As superlattice and their effects on electronic properties. The results show that the interstitial defects and Frenkel pair defects are relatively difficult to form, while the antisite defects are favorably created generally. Besides, the existence of point defects generally modifies the electronic structure of GaAs/Al_(0.5)Ga_(0.5)As superlattice significantly, and most of the defective SL structures possess metallic characteristics. Considering the stability of point defects and carrier mobility of defective states,we propose an effective strategy that AlAs, GaAs, and AlGaantisite defects are introduced to improve the hole or electron mobility of GaAs/Al_(0.5)Ga_(0.5)As superlattice. The obtained results will contribute to the understanding of the radiation damage effects of the GaAs/AlGaAs superlattice, and provide a guidance for designing highly stable and durable semiconductor superlattice-based electronics and optoelectronics for extreme environment applications.

Density Functional Theory Study on Organic Dye Sensitizers Containing Bis-dimethylfluorenyl Amino Benzofuran

The geometries, electronic structures, polarizabilities and hyperpolarizabilities, as well as the UV-Vis spectra of the two organic dye sensitizers containing bis-dimethylfluorenyl amino benzofuran were studied via density functional theory （DFT） and time-dependent DFT. The features of electronic absorption spectra were assigned on account of the agreement between the experiment and the calculations. The absorption bands in visible region are related to photoinduced electron transfer processes, and the dimethylfluorenyl amino benzo[b]furan groups are major chromophore that contributed to the sensitization of photo-to-current conversion. The role of vinylene group in geometry, electronic structure and spectra property is analyzed according to the comparative study of the dyes.

Simulated Equations of State of MgSiO3 Perovskite

The equation of state of MgSiO3 perovskite under high pressure and high temperature is simulated using the molecular dynamics method. It was found that the molecular dynamics simulation is very successful in accurately reproducing the measured molar volumes of MgSiO3 perovskite over a wide range of temperatures and pressures. The simulated equation of state of MgSiO3 perovskite matched experimental data at up to 140GPa at 300K, as well as the fitting data of others and results from the first-principles simulation based on the local density approximation. The simulated equations of state of MgSiO3 perovskite at higher temperatures and higher pressures also correspond to the other calculations. In addition, the volume compression data of MgSiO3 perovskite is simulated up to 120 GPa at 300, 900, 2000 and 3000 K, respectively.