Microstructure and lattice strain control towards high-performance ambient green-printed perovskite solar cells

Solution-processed perovskite solar cells (PSCs) have made great progress in past years. However, most fabrication methods of PSCs in the lab cannot be directly transferred to industrial printing, and the toxic volatile processing solvents are hazardous to human health and environment. Here, we demonstrate ambient green-solvent printing for high-performance methylammonium lead iodide-based perovskite solar cells enabled by a well-regulated microstructure and lattice strain in a printed perovskite layer. A smooth and uniform perovskite layer can be obtained from green solventsviacontrolling the wetting and spreading of viscous perovskite precursor ink on the hot substrate. The residual lattice strain in the hot-printed perovskite layer was effectively decreased with addition of methylammonium bromide additive, which also largely increased the perovskite grain size. This morphological improvement contributes to decreased defect density, improved charge transport and suppressed charge recombination. As a result, the solar cell based on ambient green-solvent printed key layers achieves an efficiency as high as 20.21% (average efficiency of 19.27%). The demonstration of ambient green printing and lattice strain control for high-quality printed layer paves the way towards the future commercialization of PSCs.