A numerical analysis of ZnTe/AZO as tunnel junction in CdTe/Si tandem solar cell

Abstract

Recently, interest has shifted towards developing multijunction or tandem solar cells due to their high potential to generate higher efficiency than traditional single-junction solar cells. Cadmium telluride (CdTe) and silicon (Si) solar cell materials have demonstrated significant potential in photovoltaic energy generation as tandem structures if fully developed. One approach for optimising CdTe/Si is to develop an effective tunnel junction that can electrically and optically interconnect the cadmium telluride and silicon cells with minimal loss. The wxAMPS 3.0 numerical simulation was used in this work to develop CdTe/Si tandem using zinc telluride/aluminium doped zinc oxide (ZnTe/AZO) as a tunnel junction (TJ). The result obtained shows an optimum efficiency of over 36 % with Voc = 1.945 V, Jsc = 21.519 mA/cm2, and FF = 86.823 % utilising the optimal 200 nm CdTe and Si absorber thickness of 300 μm. An analysis of the demonstrated results suggests that ZnTe/AZO tunnel junction will significantly contribute to the realisation of the CdTe/Si tandem solar cell. Hence, upon inserting a 40 nm highly doped ZnTe/AZO tunnelling junction to a CdTe/Si tandem configuration, the solar cell’s performance was enhanced by 48.190%.

Exploring the impact of defect energy levels in CdTe/Si dual-junction solar cells using wxAMPS

“…In this work, a highly doped p++ zinc telluride (ZnTe) and n++ aluminum doped zinc oxide (AZO) (ZnTe/AZO) is proposed as TJ to connect the two subcells. The doping concentrations are 10 20 cm −3 and 10 19 cm −3 for ZnTe and AZO, respectively 39 . These high doping concentrations resulted in significant bending of the Ec of ZnTe towards the Ev of AZO to ease non-local band-to-band tunneling between the top and the bottom cells, as seen in Fig.…”