A Soft Nonpolar-Soluble Two-Dimensional Perovskite for General Construction of Mixed-Dimensional Heterojunctions

Constructing mixed-dimensional heterojunctions through ion exchange between functional organic ammonium halides and the already-deposited bulk 3D perovskite films is a widely adopted strategy to effectively passivate and stabilize perovskite solar cells (PSCs). Such process poses challenges in precisely controlling the composition and distribution of the heterojunctions across the film, in particular for large-area applications. Here, a soft 2D perovskite based on tetrapheptyl-ammonium iodide (TPAI), noted as TPA₂PbI₄ is reported. It is the first-reported nonpolar readily soluble 2D perovskite, leading to highly compact and oriented perovskite layers. In addition, this nonpolar soluble TPA₂PbI₄ is beneficial to universally construct thickness-controllable mixed-dimensional perovskite heterojunctions to suppress the non-radiative recombination and promote charge-carrier transfer on all the FA-, MA- and CsPbI₃ PSCs. Such a unique strategy is also suitable for upscaling fabrication, demonstrated by 30 cm × 30 cm FAPbI₃ perovskite submodules with a certified efficiency of 22.06%.