Characteristics
of a Silicon Nanowires/PEDOT:PSS Heterojunction and Its Effect on
the Solar Cell Performance
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Abstract
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 <i>J</i><sub>SC</sub> and <i>V</i><sub>OC</sub> on the junction characteristic is discussed