Carbon Nanotube Electrode-Based Perovskite–Silicon Tandem Solar Cells

Carbon nanotube electrode–laminated perovskite solar cells in combination with n-type tunnel oxide–passivated contact silicon solar cells demonstrate a high power conversion efficiency (PCE) of 24.42% when stacked in tandem. This is compared with conventional indium tin oxide/MoO_x-deposited perovskite solar cells which give an efficiency of 22.35% when stacked in the same four-terminal tandem system. Despite higher transmittance of the carbon nanotube electrode than that of the indium tin oxide/MoO_x in the infrared range, the carbon nanotube electrode-laminated devices show lower transmittance in the same region due to the total internal reflection and scattering as evidenced by optical simulation. Yet, the exceptionally high PCE of the carbon nanotube electrode-laminated semitransparent devices far exceeding than that of the indium tin oxide/MoO_x-deposited semitransparent top cell outweighs the effect of the optical transparency. Four types of silicon solar cells are compared as the bottom subcells, and the n-type tunnel oxide-passivated contact silicon solar cells are the best choice mainly due to their high absorption in the long-wavelength region. The obtained 24.42% efficiency is one of the high PCEs among the reported four-terminal perovskite–silicon solar cells, and this article is the first demonstration of the carbon nanotube electrode application in tandem solar cells.