Mechanism of the Dimethylammonium Cation in Hybrid Perovskites for Enhanced Performance and Stability of Printable Perovskite Solar Cells

Upscaling efficient and stable perovskite materials is vital for metal halide perovskite solar cells (PSCs) and additive engineering contributes a lot to making high‐quality PSCs. While the recent examples involved mixing dimethylammonium (DMA) cation has been employed for the fabrication of all‐inorganic perovskites with improved efficiency and stability, the role of DMA cation in hybrid perovskite (formamidinium lead triiodide, denoted as FAPbI 3 ) remains inconclusive. Herein, DMA cations are substituted for FA sites of Cs 0.12 FA 0.88 PbI 3 for printable triple mesoscopic PSCs and shed lights on the roles and mechanism of DMA in the perovskite. It is found that a small amount of DMA is doped into the perovskite lattices, meanwhile, an intermediate compound DMAPbI 3 is formed and exists at grain boundaries, which improves the crystallinity of perovskite films and reduces nonradiative recombination through a passivation role. With these benefits, the best‐performing printable PSC attained a power conversion efficiency of 17.46%. Unencapsulated devices maintained over 96% of the initial efficiencies in ambient condition for 960 h and 95% of the initial efficiencies after 360 h under continuous thermal aging at 85 °C in N 2 atmosphere.