The interfacial energy-level alignment of a silicon nanowires (SiNWs)/PEDOT:PSS heterojunction is investigated using Kelvin probe force microscopy. The potential difference and electrical distribution in the junction are systematically revealed. When the PEDOT:PSS layer is covered at the bottom of the SiNW array, an abrupt junction is formed at the interface whose characteristics are mainly determined by the uniformly doped Si bulk. When the PEDOT:PSS layer is covered on the top, a hyperabrupt junction localized at the top of the SiNWs forms, and this characteristic depends on the surface properties of the SiNWs. Because the calculation shows that the absorption of light from the SiNWs and the Si bulk are equally important, the bottom-coverage structure leads to better position matching between the depletion and absorption area and therefore shows better photovoltaic performance. The dependence of JSC and VOC on the junction characteristic is discussed.
The relationship between oil prices and stocks is an important issue for portfolio selection and risk management. This article proposes a mixed frequency data sampling copula model with explanatory variables that incorporates low-frequency explanatory variables into a high-frequency dynamic copula model. It enables us to investigate the impacts of economic factors on the relationship between oil and stocks. It is found that the dependence of oil and stock markets is influenced by aggregate demand and stock-specific negative news. The impact of aggregate demand lasts for two years, while the impact of stock-specific news lasts for one quarter.
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