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Quinoxaline-based small molecules: synthesis and investigation on their optoelectronic properties

Deng J., Tao Q., Yan D., Huang X., Liao Y.

Materials Science Poland

2018

Vol. 36, No. 2

167--176

Small molecules of ThQuTh, CzQuTh, CzQuCz and TPAQuCz were designed and synthesized, based on quinoxaline acceptor, and electron donating groups, i.e. alkyl-thioephene, carbazole and triphenylamine on both side chains and molecular backbones. Their thermal, optical and electrochemical properties were systematically compared and studied. The absorption spectra of the small molecules were strongly affected by the donor units attached to quinoxaline. Strong electron donating groups, such as carbazole on the molecular backbone would lower optical band gap, resulting in a wide absorption and the strong donor on the side chain would enhance the absorption intensity in short wavelength region. The highest occupied molecular orbital (HOMO) energy levels of the four molecules were up-shifted with increasing the electron donating properties of donor units. The bulk-heterojunction organic solar cells with a device structure of ITO/PEDOT:PSS/SMs:PC61BM/LiF/Al were fabricated, in which the small molecules functioned as donors while PC61BM as acceptor. Because the electron-donating ability of carbazole (Cz), triphenylamine (TPA) is higher than that of thiophene (Th), CzQuTh, CzQuCz and TPAQuCz show higher power conversion efficiency (PCE) than that of ThQuTh. Furthermore, being the strongest in absorption intensity and widest in absorption spectrum, TPAQuCz has the highest power conversion efficiency. Further improvement of the device efficiency by optimizing the device structure is currently under investigation

Study on breakdown delay characteristics based on high-voltage pulse discharge in water with hydrostatic pressure

Yan D., Bian D. C., Ren F., Yin C. Q., Zhao J. C., Niu S. Q.

Journal of Power Technologies

2017

Vol. 97, nr 2

89--102

Significant breakdown delay occurs during high-voltage pulse discharge in water with hydrostatic pressure; this phenomenon contributes to an assessment of the stability of discharge. Monitoring discharge effect is also an important approach in engineering. However, only a few studies have reported related influencing factors. This study established an equivalent circuit of a high-voltage pulse discharge based on gasification-ionization of plasma channels to study characteristics of high-voltage pulse discharge breakdown in water with high hydrostatic pressure. Simulation calculation of channel resistance was conducted using experimental data under different hydrostatic pressure and voltage conditions. The discussions in this paper center on the influencing mechanisms of hydrostatic pressure and voltage in breakdown delay. The results show that higher voltage leads to shorter breakdown delay. Equivalent resistance decreases with increasing voltage. High voltage can enhance the degree of ionization in plasma channels, which accelerates the velocity of the ionization current, shortening breakdown delay. Higher hydrostatic pressure results in longer breakdown delay. Equivalent resistance increases with increasing hydrostatic pressure. High hydrostatic pressure inhibits section areas of the plasma channel, slowing down the velocity of the ionization current and prolonging breakdown delay. This study provides theoretical guidance for monitoring analysis of high-voltage pulse discharge in engineering and studies on breakdown delay characteristics in pulse discharges.