界面电子结构对核壳量子点/聚乙烯纳米复合绝缘电导与空间电荷特性的影响

Effect of interfacial electronic structure on conductivity and space charge characteristics of core-shell quantum dots/polyethylene nanocomposite insulation

为研究核壳量子点的界面电子结构对聚乙烯绝缘电导与空间电荷特性的影响,分别制备了CdSe@ZnS/LDPE,ZnSe@ZnS/LDPE两种核壳量子点纳米复合绝缘,研究了复合绝缘的直流电导和空间电荷的演变规律,并分析了核壳量子点的界面电子结构对电荷陷阱分布特性的影响机理.研究发现,相比于LDPE绝缘,ZnSe@ZnS/LDPE复合绝缘在高温强场条件下直流电导率可降低47.2%,空间电荷积累量降低了40.3%,且陷阱能级增大,表现出对载流子更强的捕获作用.基于密度泛函理论,计算了核壳量子点与聚乙烯绝缘的能带特征.结果表明,核壳纳米量子点的核层-壳层界面、壳层-绝缘界面的能带偏移导致导带底与价带顶发生突变,分别对电子和空穴具有限域作用,且限域效应随着量子点核层与壳层带隙差异增大而逐渐增强,从而限制高温强场下载流子迁移、抑制空间电荷积聚.

To investigate the effect of the interface electronic structure of core-shell quantum dots on the conductivity and space charge characteristics of polyethylene insulation,nanocomposite insulations,namely CdSe@ZnS/LDPE and ZnSe@ZnS/LDPE,are synthesized.The study focuses on elucidating the evolution patterns of DC conductivity and space charge in the nanocomposite insulation,and analyzing the effect of the interfacial electronic structure of core-shell quantum dots on the distribution of charge traps.Comparative analysis reveals that in contrast to LDPE insulation,ZnSe@ZnS/LDPE nanocomposite insulation demonstrates a substantial reduction in DC conductivity by 47.2% and a decrease in space charge accumulation by 40.3% under the conditions of elevated temperature and strong electric field.The increase of trap energy level means an enhanced trap effect on charger carriers.According to density functional theory,the band structure characteristics of core-shell quantum dots integrated with polyethylene are computationally assessed.The findings underscore that the band misalignment at the core-shell interface and the shell-insulation interface induces shifts in the conduction band bottom and at the valence band top,respectively.These shifts impose a confinement effect on electrons and holes,with the extent of this effect escalating with the augment of the difference in band gap between the core layer and the shell layer.Consequently,this phenomenon curtails carrier migration,thereby inhibiting space charge accumulation under the conditions of elevated temperature and strong electric fields.