Optical and electrical design guidelines for ZnO/CdS nanorod-based CdTe solar cells.

Abstract

An alternative structure to planar CdTe solar cells is realized by coating ZnO/CdS nanorods (NRs) with a CdTe layer. These structures are expected to achieve high-powered conversion efficiencies through enhanced light absorption and charge carrier collection. ZnO NR-based CdTe solar cell efficiencies; however, they have remained well below their planar counterparts, thus hindering NRs in CdTe solar cells' advantages. Here, we analyze the light trapping and carrier collection efficiencies in two types of ZnO NR-based CdTe solar cells through optical and electrical simulations. The buried CdTe solar cells are formed by completely filling the gaps in between ZnO/CdS NRs. This produces a maximum achievable photo-current of 27.4 mA/cm2 when 2000 nm-tall and 20̊-angularly-deviated NRs are used. A short-circuit current density of 27.3 mA/cm2 is achievable with the same geometry for 5 rods/μm2-dense NRs when a moderate CdTe doping density and a CdS/CdTe surface velocity of 1016 cm-3 and 104 cm/s are used, respectively. We reveal the potential of buried CdTe solar cell for high-charge carrier collection and provide a design guideline in order to achieve high short-circuit current densities with ZnO NR-based CdTe solar cells.