Yuhang Xu

An investigation on two-phase mixture discharges: the effects of macroparticle sizes

A two-phase mixture (TPM) is a mixture of gas and macroparticles of high concentration, and there has been significant interest in many technical applications and natural phenomena concerning two-phase mixture discharges (TPMDs), but until now there has been no widely accepted analysis for the propagation of discharges in TPMs. In this paper, 21 kinds of different dielectric materials are used to investigate the effects on TPMD. The diameters of macroparticles in 21 kinds of TPMs are measured by microscope, laser particle size analyzer, etc, and the volume fractions are measured by a video camera and particle image velocimetry system. Based on a direct comparison of the breakdown voltages and the percentages of the discharge path in TPMs with those in air, this work reveals that whether TPMs promote the discharge development or not depends mainly on the macroparticle sizes. These macroparticles in TPMs distort the electric field, interact with ions, electrons or photons, and produce corresponding enhancements or decreases in ionization and excitation as the streamer front encounters them, but the details of alterations on the discharge development are highly correlated with the macroparticle sizes.

Nanotube enhanced carbon grids as top electrodes for fully printable mesoscopic semitransparent perovskite solar cells

Semitransparent solar cells have attracted significant attention for their potential applications, though obtaining high average visible transmittance (AVT) while maintaining good conversion efficiency is a challenge. Here, we report a method to fabricate fully printable semitransparent perovskite solar cells with a (5-AVA)0.05(MA)0.95PbI3 infiltrated mesoporous TiO2/Al2O3/carbon architecture. Carbon grids were printed as top electrodes, and the effects of the grid spacing on device performance were systematically investigated. Under the smallest grid spacing, the highest power conversion efficiency (PCE) of 11.31% was achieved, though the AVT was low. By adjusting the grid spacing, the highest AVT of 26.4% was obtained, though the PCE dropped to 5.36%. A thin layer of multi-walled carbon nanotubes (MWCNTs) was then introduced on the top electrode, which improved both the conductivity and charge transfer characteristic of the electrode, resulting in a high PCE of 8.21% while maintaining a good AVT of 24.0%.

Initiation and Propagation of Discharge in Liquid Droplets: Effect of Droplet Sizes

Three kinds of water mist with different droplet sizes are applied to understand the effect of droplet sizes on the initiation and propagation of discharges in a nonuniform field at atmospheric pressure. Based on the measurement of droplet sizes in three mists and the volume fraction of water droplets, effect of droplet sizes is demonstrated by directly comparing the percentages of the discharge path in mist at the different positions with those in air. It can be concluded that the mist with smaller μm-droplets has the negative impact on the initiation and propagation of discharges; the mist with larger μm-droplets has the inhibited effect on the starting and growth of positive discharge but has the contrary effects on negative discharge.

Influence of waterdrop sizes on the growth of discharge

Streamer is not only the prelude of leader discharge development, but also the important stage of lightning. In order to understand the influence of water droplet sizes on the initiation and growth of discharge, three kinds of mist with different size droplets are applied to study this influence. Based on the measurement of droplet sizes in three mist and directly comparative analyses of the percentages of the discharge path on mist or air in a non-uniform field, at atmospheric pressure, it can be concluded that mist with droplets smaller than 10 µm suppresses the lightning discharge, and has the negative impact on the first step of discharge; mist with droplets greater than 10 µm has the inhibited effect on the starting and growth of positive discharge, but has the contrary effects on negative discharge. These droplets in mist distort the electrostatic field, interact with ions, electrons or photons, and produce corresponding enhancements or decreases in ionization and excitation as the avalanche front encounters them, but the details of different degree alterations on avalanches highly correlate with the droplet sizes.