Solution-processed Cu(In,Ga)(Se,S)2 solar cells prepared via a surface sulfurization process

Towards All-Non-Vacuum-Processed Photovoltaic Systems: A Water-Based Screen-Printed Cu(In,Ga)Se2 Photoabsorber with a 6.6% Efficiency

During the last few decades, major advances have been made in photovoltaic systems based on Cu(In,Ga)Se₂ chalcopyrite. However, the most efficient photovoltaic cells are processed under high-energy-demanding vacuum conditions. To lower the costs and facilitate high-throughput production, printing/coating processes are proving to be effective solutions. This work combined printing, coating, and chemical bath deposition processes of photoabsorber, buffer, and transparent conductive layers for the development of solution-processed photovoltaic systems. Using a sustainable approach, all inks were formulated using water and ethanol as solvents. Screen printing of the photoabsorber on fluorine-doped tin-oxide-coated glass followed by selenization, chemical bath deposition of the cadmium sulfide buffer, and final sputtering of the intrinsic zinc oxide and aluminum-doped zinc oxide top conductive layers delivered a 6.6% maximum efficiency solar cell, a record for screen-printed Cu(In,Ga)Se₂ solar cells. On the other hand, the all-non-vacuum-processed device with spray-coated intrinsic zinc-oxide- and tin-doped indium oxide top conductive layers delivered a 2.2% efficiency. The given approaches represent relevant steps towards the fabrication of sustainable and efficient Cu(In,Ga)Se₂ solar cells.

Eco-friendly and cost-efficient inks for screen-printed fabrication of copper indium gallium diselenide photoabsorber thin films

Given the societal concerns about the use of toxic chemicals and costly fabrication of functional materials and devices for photovoltaic applications, it is important to develop alternative sustainable methodologies. Previous studies have shown that cost-effective printing fabrication of Cu(In,Ga)Se₂ thin film photovoltaics represents an interesting alternative to energy-demanding vacuum-based deposition methods, commonly used to produce Cu(In,Ga)Se₂ photovoltaics. To enrich the field of printed Cu(In,Ga)Se₂ photoabsorber thin films and to develop associated eco-friendly solutions, two novel inks, consisting of non-toxic reagents and readily available oxide materials, are reported. Screen printing of the inks over fluorine-doped tin oxide conductive substrates followed by swift selenization of the resultant patterns provides a straightforward route to phase-pure, uniform, and compact Cu(In,Ga)Se₂ films with thickness and band gap energies ranging from 2.5 µm to 3.5 µm and from 0.97 eV to 1.08 eV, respectively. The present approach represents an important step forward in the sustainable fabrication of Cu(In,Ga)Se₂ photovoltaics, where the physical properties of the photoabsorber can be easily adjusted by tuning the conditions of the screen printing process and the metal ratios in the inks.