Ultrathin transparent metal capping layer on metal oxide carrier-selective contacts for Si solar cells

Carrier-selective contacts using metal oxide thin films have been proposed and successfully demonstrated for dopant-free Si solar cells. However, the electronic properties of several metal oxide thin films such as MoOx can deteriorate easily due to the modification of surface chemical state upon exposure to ambient air. Here, we report the use of an ultrathin Au capping layer on MoOx to mitigate the undesired surface chemistry modification. In addition, the Au capping layer also functions as a transparent conducting electrode, thereby potentially allowing the replacement of transparent conductive oxides such as indium tin oxide. We further show that the power conversion efficiency of a simple Au/MoOx/n-Si device increases from 0.53 to 6.43% with the incorporation of a grid type electrode at the front surface. Our results provide insights into the design of efficient solar cells incorporating carrier selective contacts without the need to use transparent conductive oxides.