We report a novel approach for a fast phase transition of FAPbI₃ (FA = formamidinium) at low-temperature and the effective removal of interfacial recombination in MAPbI₃ (MA = methylammonium). This method also allows for printing (patterning) of the perovskite on a desired area. The pre-annealed MAPbI₃ and δ-phase FAPbI₃ films were prepared by spin-coating DMSO and a polar aprotic solvent admixed precursor solution at 65 °C and 100 °C for about 1 min, respectively, to form adduct films containing DMSO. Two films were sandwiched without pressure by a method called bifacial stamping, and annealed at 100 °C for 9 min, which resulted in complete δ → α phase transition of FAPbI₃ and led to a power conversion efficiency (PCE) of 18.34%. The stamped MAPbI₃ demonstrated a PCE of 20.18% that was much higher than the conventionally annealed MAPbI₃ (∼17.4%) mainly due to a much higher fill factor and open-circuit voltage. Optical and structural studies revealed that DMSO-mediated ion exchange plays a vital role in the phase transition of FAPbI₃ and the surface modification of MAPbI₃. Theoretical calculation results further support the role of DMSO in the phase transition at low temperature. Stamping was applied to EAPbI₃ (EA = ethylammonium), where photoinactive yellow EAPbI₃ changed to photoactive EAPbI₃ with a PCE of 13.02% after stamping with MAPbI₃. The DMSO-mediated EA/MA ion exchange reaction during the stamping process created a new layer having a gradient solid solution of EAPbI₃ and MAPbI₃, which was responsible for the abnormally high PCE of the EAPbI₃ based perovskite solar cell. Facilitated ion transport by a Lewis base (such as DMSO) reservoir in the perovskite adduct film is suggested to be involved in the bifacial stamping procedure.

中文翻译：

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用于高效钙钛矿太阳能电池的双面冲压†

我们报告了一种新颖的方法，用于在低温下快速转变FAPbI ₃（FA = Formamidinium ），并有效去除MAPbI ₃（MA =甲基铵）中的界面重组。该方法还允许将钙钛矿印刷（图案化）在期望的区域上。通过分别在65°C和100°C下分别旋涂DMSO和极性非质子溶剂混合前驱体溶液约1分钟来制备预退火的MAPbI ₃和δ相FAPbI ₃膜，以形成包含DMSO的加成膜。通过双面冲压的方法在无压力的情况下将两层膜夹在中间，并在100°C下退火9分钟，从而导致FAPbI ₃完全δ→α相变功率转换效率（PCE）为18.34％。冲压后的MAPbI ₃的PCE为20.18％，比传统退火的MAPbI ₃（〜17.4％）高得多，这主要是由于填充系数和开路电压高得多。光学和结构研究揭示，DMSO介导的离子交换起着FAPbI的相变至关重要的作用₃和MAPbI的表面改性₃。理论计算结果进一步支持了DMSO在低温相变中的作用。对EAPbI ₃（EA =乙基铵）进行压印，其中无光黄色EAPbI ₃变为光敏EAPbI ₃用MAPbI ₃压模后的PCE为13.02％。在冲压过程中，DMSO介导的EA / MA离子交换反应产生了一个新层，该层具有EAPbI ₃和MAPbI ₃的梯度固溶体，这是基于EAPbI ₃的钙钛矿太阳能电池异常高PCE的原因。钙钛矿加合物膜中的路易斯碱（例如DMSO）储层促进的离子迁移被认为参与了双面冲压过程。