Design of novel type-I (type-II) band alignment in GeC-VXY (V = Cl, Br; Y = Se, Te) van der Waals heterostructure for optoelectronic and renewable energy application

Van der Waals heterostructure (vdWH) of two dimensional (2D) materials exhibit abundant physical properties as well as important applications in nanoelectronics, optoelectronics, photocatalysis and renewable energy. Here, we investigate optoelectronic and photocatalytic properties of vdWH GeC-VXY (X = Cl, Br; Y = Se, Te) by performing density functional calculations. Different staking models and stabilities of the vdWH are compared. Our calculated results confirms that GeC-VClSe (GeC-VBrSe) vdWH for model-I and II have direct type-II band alignment, playing crucial rule in light harvesting and detection; while the remaining vdWH have indirect band gaps with type-I band alignment. Optical properties in term of imaginary part of dielectric function have also been calculated, which show that all the first exitonic peaks lies in the visible region and also blue shifts are observed in vdWH. In the last we have calculated the photocatalytic properties of GeC-VXY (X = Cl, Br; Y = Se, Te) vdWH and found to be a potential photocatalytic for full water splitting at pH = 0.