Dynamic casting in combination with ramped annealing process for implementation of inverted planar Ag3BiI6 rudorffite solar cells

Abstract

The use of toxic Pb and insufficient long-term stability continue to limit the commercialization of organic-inorganic hybrid perovskite photovoltaics despite their excellent power conversion efficiencies (PCEs). Inorganic silver bismuth iodide is a strong candidate for a Pb-free and stable light harvester. Using a conventional n-i-p structure with high-temperature-processed TiO2 charge transport layer, PCEs of more than 4% have been achieved. However, development of inverted planar p-i-n architecture supporting low-temperature flexible application are still in its infant stage as the PCE of only 0.02% has been reported. To unravel such poor performance of the p-i-n structure, a Ag3BiI6 rudorffite film has been fabricated using a combination of dynamic casting (DC) and ramped annealing (RA). This technique significantly enhances the surface coverage of Ag3BiI6 on the underlying planar NiOx hole collector. Furthermore, the optimal annealing temperature of 180 degrees C allows for the formation of a highly polycrystalline and dense absorber. Based on this approach, the unprecedented PCE of 1.08% has been achieved, whereas the conventional method gives the PCE of only 0.07%. The DC/RA method could offer a new perspective for developing Pb-free inorganic rudorffite photovoltaics with an inverted planar architecture.