Merging solution processing and printing for sustainable fabrication of Cu(In,Ga)Se2 photovoltaics

Abstract

The targeted global decarbonization demands the urgent replacement of conventional fossil fuel with low carbon technologies. For instance, solar energy is abundant, inexhaustible, non-polluting, and low-priced; however, to produce energy on a large scale with reliable, cost-efficient, and environmentally friendly methods remains a challenge. The outstanding optical properties of Cu(In,Ga)Se2 thin film photovoltaics and their intrinsic compatibility with industrial-scale production are paving the way towards this technology. However, most of the activity in the field relies on the use of non-environmentally friendly methodologies to achieve solution-processed flexible and lightweight photovoltaics with significant efficiencies. Importantly, there is a search for more sustainable alternatives that are compatible with roll-to-roll industry to improve the cost-effectiveness and sustainability of photovoltaics without compromising the photovoltaic performance. Herein, we review cost-efficient and sustainable fabrication methodologies that complement the current high- energy-demanding vacuum-based fabrication of Cu(In,Ga)Se2 photovoltaics. The existent non-vacuum deposition methods of Cu(In,Ga)Se2 photoabsorbers are presented and precursors and solvents used in ink formulations are discussed in terms of sustainability. The approaches resulting in most efficient photovoltaic cells are highlighted. Finally, all-solution-processed Cu(In,Ga)Se2 photovoltaics are reviewed, along with the non-vacuum deposition methods of the individual layers, contributing to an even higher throughput and low-cost production. This review highlights the relevance and potential of sustainable non-vacuum methodologies, as well as the need of further investigation in this field to ultimately give access to high-end CIGS PVs with low-cost fabrication.