Design and numerical optimisation of a CH3NH3SnI3−x Br x /CI(G)S tandem solar cell with over 50% PCE

Abstract This work proposes and numerically optimises a four terminal mechanically stacked tandem with CuI/CH 3 NH 3 SnI 3− x Br x /ZnO:Al/IZO as top subcell and IZO/GaSe/CI(G)S/CIGS-P + as bottom subcell. The standalone optimised subcells exhibited power conversion efficiencies of 27.03% (CH 3 NH 3 SnI 3 based cell) and 24.42% (CIGS based cell), with the tandem configuration showing a combined power conversion efficiency of 51.45%. Band gap optimisation of the CIGS based solar cell also revealed that its gallium content had to be nullified, which is a favourable outcome considering the high cost of gallium. Furthermore, the tandem device also exhibited excellent quantum efficiency while spanning the UV-Vis-NIR range of photon wavelength absorption, as a result of the CI(G)S based subcell complementing the top CH 3 NH 3 SnI 3 based subcell.