Efficient and stable formamidinium-caesium perovskite solar cells and modules from lead acetate-based precursors

Controlling the crystallization process of perovskite thin films to obtain a high-quality material is one of the most challenging aspects for upscaling perovskite solar cell (PSC) technology. The use of non-halide lead sources, such as lead acetate, is a potential solution to this issue due to the fast perovskite crystallization process triggered by the facile removal of acetate during post-annealing. However, to date, lead acetate has been used exclusively as a precursor for the synthesis of methylammonium (MA) or caesium (Cs) based perovskites, which are unstable and less efficient. Here, we expand the lead acetate precursor route to form mixed A-cation perovskites, namely, formamidinium-caesium lead perovskite. High-quality large-area formamidinium-caesium mixed-cation perovskite films were produced by blade-coating a lead acetate-based precursor formulation in an ambient laboratory environment, with the use of NH4+ as a volatile cation to drive off acetate during annealing, leading to formation of PSCs with a power conversion efficiency (PCE) of up to 21.0%. Blade coated mini-modules with an aperture area of 10 cm(2) displayed PCEs of up to 18.8%. The encapsulated PSCs showed excellent thermal stability, with no evidence of efficiency loss after 3300 hours at 65 degrees C.

Automated summary

Controlling the crystallization process of perovskite thin films is crucial for enhancing the quality and efficiency of perovskite solar cells. This study explores the use of lead acetate as a precursor to form mixed A-cation perovskites and achieves high-quality films with a power conversion efficiency of up to 21.0%. The developed method shows great potential in upscaling perovskite solar cell technology.