Numerical analysis of the back interface for high efficiency wide band gap chalcopyrite solar cells

•The properties of the back interface of wide band gap CIGS solar cells is investigated by SCAPS-1D.•MoO3 interfacial layer with high work function is effective to reduce the schottky barrier.•The performances of the device are enhanced by reducing back barrier and interface recombination.•24% efficiency CIGS solar cells can be achieved using sub micrometer thick absorber.