GaAs Nanowire Array Solar Cells with Axial p–i–n
Junctions
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Abstract
Because of unique structural, optical,
and electrical properties,
solar cells based on semiconductor nanowires are a rapidly evolving
scientific enterprise. Various approaches employing III–V nanowires
have emerged, among which GaAs, especially, is under intense research
and development. Most reported GaAs nanowire solar cells form p–n
junctions in the radial direction; however, nanowires using axial
junction may enable the attainment of high open circuit voltage (<i>V</i><sub>oc</sub>) and integration into multijunction solar
cells. Here, we report GaAs nanowire solar cells with axial p–i–n
junctions that achieve 7.58% efficiency. Simulations show that axial
junctions are more tolerant to doping variation than radial junctions
and lead to higher <i>V</i><sub>oc</sub> under certain conditions.
We further study the effect of wire diameter and junction depth using
electrical characterization and cathodoluminescence. The results show
that large diameter and shallow junctions are essential for a high
extraction efficiency. Our approach opens up great opportunity for
future low-cost, high-efficiency photovoltaics