Alkyl Additive‐Mediated Growth of Two‐Dimensional Tin Halide Perovskites for Efficient Charge Transport

Solution‐processed two‐dimensional (2D) tin (Sn 2+ )‐halide perovskites have achieved great milestones in (opto)electronic devices. The fabrication of high‐quality 2D Sn 2+ ‐halide perovskite films has remained a difficult challenge due to the Lewis acidity of Sn 2+ and its rapid crystallization. Herein, incorporating an alkyl additive, 1,8‐diiodooctane (DIO), to mediate growth of 2D Sn 2+ ‐halide perovskites by chelating with tin‐iodide [SnI 6 ] 4− inorganic octahedral cage at the intermediate iodide vacancies is suggested. The chelation of DIO and 2D Sn 2+ ‐halide perovskites promotes deceleration of film crystallization, producing high‐quality films with homogeneous connection of lattice aligned parallel to the substrates. The optimized DIO‐incorporated 2D Sn 2+ ‐halide perovskite transistors and phototransistors demonstrate more than twofolds the field‐effect mobility compared to pristine devices, enhanced operational stability, and optoelectronic conversion ability. The incorporation of DIO facilitates the optimal growth of homogeneous 2D Sn 2+ ‐halide perovskite films for emerging halide perovskite‐based (opto)electronics.