Optically active metal oxides for photovoltaic applications

The rising consumption of nonrenewable energy sources has posed a serious threat to the global environment and human safety. Alternative energy sources have been focused upon to tackle these problems for reliably satisfying the current energy demands. In recent years, the photovoltaic industry has emerged as a promising alternative source as it is based on renewable energy of the sun that is abundant, clean, and inexhaustible. The photovoltaic industry is primarily based on the use of solar cells that converts the incident photon energy into electricity using optically active semiconducting materials. The optically active materials form the backbone of solar cells as they accomplish the desired energy conversion activity. Out of the commonly used optical materials (sulfides, selenides, tellurides, and oxides), metal oxides have garnered significant research attention due to their unique optical, electrical, chemical, and structural properties. These unique properties have enabled metal oxides to demonstrate versatile function in various types of solar cells (first-, second-, and third-generation). The metal oxides have efficiently demonstrated their performance as back contacts, absorbers, buffers layers, and transparent conductive oxide (TCO) layers. Furthermore, by strictly adhering to the photovoltaic objectives, that is, developing high-efficiency solar cells at a lower cost, the metal oxides are found to be the most suitable materials as they are cheap, possess easy processability, and exhibit high stability as compared to other optical materials. Hence, in the current chapter, a brief overview of the metal oxides in solar cells along with their versatile functions have been discussed. The key factors influencing the properties/performance of metal oxides along with their associated issues/solutions and potential future are highlighted.