Numerical device simulation of carbon nanotube contacted CZTS solar cells

Nanolayers of graphene and nanotubes have become the attractive materials as the front or back electrodes in thin film solar cells. We propose a novel thin-film solar cell structure in which the traditional transparent conductive oxide electrode, ZnO:Al, is replaced by a thin layer of single-wall carbon nanotubes bundle with a honeycomb network. SCAPS simulation is used to investigate the band diagram, current–voltage characteristics and quantum efficiency of this hybrid device. The advantage of embedding metallic nanotubes is the superior electrical and optical properties such as  wide and controllable work function and transparency to wider range of wavelengths as well as high charge transport conductivity. These excellent optical and electrical properties led to a better short-circuit current density and quantum efficiency in hybrid CZTS devices. In addition, we observed an improvement in open-circuit voltage of the Au:Cu doped nanotube bundles compared to undoped nanolayer network. Nanolayers do reduce the device degradation by covering the grain boundaries and surpassing the ion migration under aging conditions.