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

Abstract

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 $\hbox {MoO}_{\mathrm{x}}$ 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 $\hbox {MoO}_{\mathrm{x}}$ 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/$\hbox {MoO}_{\mathrm{x}}$/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.