An international research team has used an inkjet-printing process to fabricate formamidinium tin-lead (Sn-Pb) perovskite thin films for applications in perovskite solar cell manufacturing.
“This work represents a significant advancement in the development of lead-reduced, eco-friendly perovskite solar cells through inkjet-printing technology. Our team led by Prof. Eva Unger has focused on optimizing the inkjet-printing process to ensure precise film deposition and enhance device performance,” first author Ayush Tara, told pv magazine. “The study opens up new avenues for eco-conscious, scalable, and efficient solar energy solutions.”
The team chose inkjet-printing for the combinatorial mixed formamidinium tin-lead (Sn-Pb) film due to its “flexibility in design” and ability to “precisely adjust the crystallization properties of organohalogen perovskite layers,” in addition to a high degree of control. It is also considered to be a high-throughput manufacturing methodology as opposed to spin coating, which has enabled high-performing lab-sized devices but lacks the scaling potential.
The researchers prepared a filtered precursor perovskite ink solution before filling the Pixdro LP50 inkjet printhead in a tool supplied by Germany-based Süss Microtec. It was a Spectra SE128 printhead with 30 pL droplet size. They explained that the ink is held at an ink-head temperature of 60 C, and the printing is done with a printhead voltage of 80 V and a jetting frequency of 100 Hz, which is applied on a mobile substrate. “The best results are obtained at printing resolution of 500 dpi, quality factor 4, print speed of 100 mm/s, and drop velocity of 4m/s,” they said.
After printing, the substrates were treated with gas-flow-assisted vacuum drying, followed by thermal annealing at 100 C for 10 min. Test results showed that “incorporating Pb up to 50% into FASnI3 films enhances lattice stability.” The best-performing composition was a solar cell with an active area of 0.16 cm2, a power conversion efficiency of 10.26%, and an energy bandgap of 1.25 eV bandgap.
The team added that based on its knowledge, the performance represents the highest reported efficiency for mixed Sn-Pb-based perovskite solar cells produced through inkjet printing to date. “Additionally, these cells exhibited an absorption spectrum extending beyond 1000 nm, corresponding to a 1.25 eV bandgap,” noted the scientists, highlighting its suitability as a candidate for the narrow bandgap subcell of all-perovskite tandem solar cells. “The results suggest that inkjet printing can effectively enhance the efficiency of tin–lead-based PSCs, supporting scalability in device manufacturing,” they concluded.
The study provides a basis for further research. “The next target is to develop large-area inkjet printed tin-lead perovskite solar cells and finally to integrate them as bottom cells in all-perovskite tandem solar cells,” said Tara.
