Crystalline silicon solar cells based on poly-Si Tunnelling Oxide Passivating Contacts (TOPCon) is becoming one of the most promising solar cell structures that enable both high efficiency and low cost. The record efficiency for the Front-Back contacted (FBC) cell with TOPCon structure is 25.7 %. By moving both the metal contacts to the back side, the so-called interdigitated back contact (IBC) approach, the solar cell efficiency can be improved significantly due to the absence of optical shading from the front metal contact. Further, by narrowing the width of the metal fingers present on the rear side of an IBC solar cell, light illumination can also be made possible from the rear side. This makes the IBC solar cell a bifacial IBC solar cell. The objective of this thesis work is to optimize the Carrier Selective Passivating Contacts (CSPCs) with an ultra-thin thermal SiOX.