Ink Engineering of Inkjet Printing Perovskite.

Inkjet printing method is one of the most effective ways for fabricating large-area perovskite solar cells (PSCs). However, because ink crystallizes rapidly during printing, the printed perovskite film is discontinuous with increasing defects. It severely restricts the application of the inkjet printing technology to the fabrication of perovskite photovoltaic devices. Here, we designed a new mixed-cation perovskite ink system that can controllably retard the crystallization rate of perovskite. In this new ink system, the printing solvent is composed of n-methyl pyrrolidone (NMP) and dimethyl formamide (DMF), and PbX2 is replaced by PbX2-DMSO (X = Br, I) complex as a printing precursor to create a high-quality perovskite layer. Accordingly, the printed Cs0.05MA0.14FA0.81PbI2.55Br0.45 perovskite film exhibited high homogeneity with a large grain size (over 500 nm). Besides, the printed perovskite film possessed lower defects with improved carrier lifetime compared to the control sample. Combining these advantages, the printed PSC delivers decent power conversion efficiencies (PCEs) of 19.6% (0.04 cm2) and 17.9% (1.01 cm2). The large-area device can still retain its original efficiency of 89% when stored in air with humidity less than 20% for 1000 h.