1-己烯是生产高性能聚烯烃产品的重要单体。乙烯三聚是在2-乙基己酸铬(chromiumtri-2-ethylhexanoate,Cr（EH）)和部分水解的三异丁基铝（partially hydrolysedtri-isobutylaluminium,PIBAO）催化乙烯聚合过程中被首次发现。之后,Briggs向Cr（EH）/PIBAO体系中加入1,2-二甲氧基乙烷（1,2-dimethoxyethane,DME）使得1-己烯的选择性和活性分别提高至73%和2086g/（g Cr per hour）。据此,作者提出DME的加入使乙烯聚合活性中心转变为三聚活性中心,假设两种活性中心在转化前后的价态不变,本文设计了五组活性中心分子模型（表1）,采用密度泛函法（DFT）对DME的转化作用进行了研究,但计算结果并未与实验现象相一致。结果表明:其一,由于催化剂活化过程及活性中心状态的不确定性,实际催化体系比所采用的分子模型配体环境更为复杂;其二,聚合及三聚活性中心的价态在DME加入前后可能发生了改变。以上推断的实验和计算模拟验证工作仍在继续进行中。
Since the absorption spectra and hole mobility of conjugated polymer donor materials are the major factors that affect the power conversion efficieny(PCE) of polymer solar cells (PSCs),in order to predict absorption b...
详细信息
Since the absorption spectra and hole mobility of conjugated polymer donor materials are the major factors that affect the power conversion efficieny(PCE) of polymer solar cells (PSCs),in order to predict absorption band and the hole mobility for guiding the synthesis of novel materials with broader absorption band and higher hole mobility for improving the photovoltaic properties of the conjugated polymers,quantum-chemical techniques are employed to calculate the absorption spectra and energy gaps of benzo[1,2- b:4,5-b’]dithiophene(BDT) with different conjugated units,namely,poly(4,8-bis(dodecyloxy) benzo[1,2-b:4,5-b’]dithiophene)(H2),poly(4,8-bis(do- decyloxy) benzo[1,2-b:4,5-b’]dithiophene)-alt-(2,5-thiophene)(H6),poly(4,8-bis(dodecyloxy) benzo[1,2-b:4,5-b’]dithiophene)-alt-(2,9-thieno[3,4-b]pyrazine)(H9).In addition to HOMO-LUMO gaps(Δ),geometries optimized,electronic properties of the neutral molecules are studied using the B3LYP *** lowest excitation energies(E) and the maximal absorption wavelength(λ) of(H),(H6)and(H9) are investigated by employing time-dependent density functional theory(TD-DFT).Δ and E values of each polymer are obtained by extrapolating those of the oligomers to the inverse chain length equal to zero(1/n=0). When introduced electron-donating unit and electron-deficient unit are introduced into BDT,their energy gaps,HOMO and LUMO energy levels of the polymers are tuned *** effects lead to a reduction of the energy barrier for the injection of holes in related polymeric photovoltaic devices and should contribute to the enhancement of their performances.
暂无评论