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Triammonium Molecular Tripods as Organic Building Blocks for Hybrid Perovskite Solar Cells
Considerable efforts have been devoted to the development of new organicâinorganic hybrid perovskites as well as their passivationâlayer materials to improve the performance of solutionâprocessable thinâfilm solar cells for practical applications. For this purpose, monocations, such as monoammonium ions, have been studied extensively as organic building blocks. Herein, a new class of cationic molecules featuring a triptycene framework is introduced, to which three ammonium ions are attached close to each other. Inspired by the previous finding that 1,8,13âtrisubstituted triptycenes have an excellent ability to form 2D assemblies, two derivatives with ammonium ion groups at these positions are synthesized, linked either directly or via methylene spacers. Hybrid perovskites with different dimensionalities in terms of the inorganic octahedral units were prepared by reaction of the triammoniumâappended triptycene tripods with PbI2, however, the optoelectronic properties obtained were unsatisfactory. Even so, the triammoniumâcontaining triptycene tripod having methylene spacers was shown to serve as a good passivation layer for perovskites solar cells (PSCs), leading to improvements in power conversion efficiency and longâterm stability. Given the large degree of design freedom, triptycene tripods merit further investigation as a new motif in the development of surfaceâpassivation materials for PSCs