Triammonium Molecular Tripods as Organic Building Blocks for Hybrid Perovskite Solar Cells

Considerable efforts have been devoted to the development of new organic-inorganic hybrid perovskites as well as their passivation-layer materials to improve the performance of solution-processable thin-film 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 1,8,13-trisubstituted 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 triammonium-appended triptycene tripods with PbI2, however, the optoelectronic properties obtained were unsatisfactory. Even so, the triammonium-containing 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 long-term stability. Given the large degree of design freedom, triptycene tripods merit further investigation as a new motif in the development of surface-passivation materials for PSCs. Triammonium molecular tripods containing a triptycene skeleton were designed and examined as components for hybrid perovskites and as surface-passivating agents for a hybrid perovskite solar cell (PSC). The triptycene tripod carrying ammonium groups via a methylene spacer was shown to provide a good passivation layer for PSCs, leading to improvements in power conversion efficiency (PCE) and long-term stability.image (c) 2024 WILEY-VCH GmbH