(256e) Invited Talk: A Charge Transfer Framework That Describes Supramolecular Interactions Governing Structure and Properties of 2D Perovskites

Organometal halide perovskites can efficiently absorb light; perovskite solar cells can generate electricity with power conversion efficiencies now exceeding 25%. However, halide perovskites decompose when exposed to light, heat, or moisture, making them unsuitable for use as active components in solar cells. Two-dimensional perovskites with organic ammonium spacer ligands offer improved environmental stability, but the power conversion efficiencies of the solar cells containing these two-dimensional perovskites are low, reflecting inefficient charge transport. As the interactions between organic ligands and the perovskite octahedra affect the octahedral tilts, directly affecting charge transport, there is an opportunity for a comprehensive molecular design strategy that can manipulate organic-inorganic interactions, control octahedral tilt, enhance charge transfer, and impact device performance. In this talk, I will discuss our approach to molecular design, and using both theoretical and experimental support, elucidate the role of the organic cation in controlling the macroscopic properties of the resulting two-dimensional perovskites. Importantly, we learned that attractive point interactions within the organic bilayer result in a withdrawal of the organic cation from the interstitial site, and less penetration of the organic cation correlates to better performing solar devices. This design paradigm can guide future innovations in solution processable perovskite optoelectronics, with the goal of creating both high performing and stable next generation solar cells.