Perovskite Solar Cells (PSCs) became a game changer in photovoltaic technology and holds a great promise to reduce the cost of solar energy production. Fabrication of PSCs on flexible substrates offers a unique pathway towards manufacturing of terawatt-scale solar photovoltaic technology, it involves the fabrication of large area mass production of PSCs and modules by incredibly high throughput roll-to-roll slot-die coating method processing. Therefore, there is a great possibility of commercializing PSC technology through roll-to-roll printing method. Beyond high throughput roll-to-roll processing, flexible PSCs will also enable more diverse applications for solar energy harvesting including, their facile integration into buildings, consumer electronics, automobiles, and various other portable applications.

The feasibility of upscaling the PSC technologies to a high-volume production using roll-to-roll slot-die coating is demonstrated in this study. Several attempts were carried out to optimize the slot-die coating technique to fabricate large-area PSCs on flexible ITO-coated PET (ITO/PET) substrates. PSCs are fabricated by roll-to-roll slot die coating on flexible ITO/PET substrates with the width of 6 inches and the web speed of 2 m/min. Initially, it involves roll-to-roll deposition of SnO₂ electron transport layer (ETL), followed by a photoactive perovskite (MAPbI₃) layer at ambient conditions compatible with industrial manufacturing. These coatings were developed by optimizing an appropriate meniscus length, flow rate, and drying conditions for attaining good quality films. Intense Pulse Light (IPL) annealing method is integrated into the roll-to-roll printing, which allows rapid crystallization of SnO₂ and Perovskite films within fraction of milli seconds by using high energy pulses at different pulse intervals. It eliminates the use of conventional ovens for thermal annealing and enables cost-effective large-scale production of Perovskite films and their corresponding solar cells rapidly. As obtained films were used for n-i-p device fabrication by spinning Spiro-OMeTAD solution as a hole transporting layer (HTL) and thermal evaporation of MoOx as a buffer layer and silver (Ag) as a top contact. The average stabilized power conversion efficiency (PCE) of devices made from different areas of the large area films is more than 10.5% and obtained a champion device PCE of 11.24% with an active are of 1cm². The demonstrated achievement is very promising and paves an easy route towards future commercialization of perovskite solar cell technology via roll-to-roll slot-die coating method.

On a different approach for the first time, we demonstrated the deposition of non-aqueous SnO₂ as an ETL over the active perovskite film and the corresponding p-i-n configuration of deices were fabricated. In which, SnO₂ nanoparticles were functionalized with acetate groups through ligand exchange and in addition, it does not require high temperature post treatment condition. Besides, low temperature processed NiOx HTL is also employed to fabricate full inorganic metal oxide p-i-n configuration of devices by eliminating organic content in either HTL or ETL for improving the stability of as fabricated PSCs. Thus, the outcome of results is promising that roll-to-roll slot-die coating method will assist in improving the large-scale production of PSCs at ambient conditions and pave the way for mass production of cost-effective PSCs and modules in near future.

Key words: roll-to-roll, slot-die, Intense Pulse Light, nickel oxide, tin oxide, perovskite solar cells