Interlayer Distance Dictates Ion Transport and Degradation in 2D Perovskites for Optoelectronic Applications
Hye-Ji Bae a, Tae-Youl Yang a
a Chungnam National University
Oral, Tae-Youl Yang, presentation 169
Publication date: 6th February 2024

Recently, two-dimensional (2D) perovskites have gained significant interest in perovskite solar cells and light-emitting diodes (LEDs) due to their combined chemical stability and tunable bandgap properties. The layer thickness and interlayer distance in 2D perovskite structures significantly influence their physical and chemical properties, such as a decreasing bandgap with increasing layer number. However, research on the dependence of ion transport properties on interlayer distance in 2D halide perovskites remains limited. This study investigates the crucial role of interlayer distance in ion transport properties of 2D perovskites. By incorporating cations of varying sizes (propylammonium iodide (PAI), hexylammonium iodide (HAI), and octylammonium iodide (OAI)), we demonstrate a strong dependence of both ionic and electronic resistivity on interlayer distance and crystallographic direction. For vertical transport (perpendicular to PbI6 layers), both resistivities increase markedly with increasing interlayer distance, with ionic resistivity exhibiting a more pronounced rise. Conversely, horizontal transport (parallel to PbI6 layers) shows decreasing ionic resistivity but increasing electronic resistivity with increasing interlayer distance. Notably, ionic resistivity and the time constant for ion migration decrease under illumination as the interlayer distance increases. This trend coincides with the observed acceleration of degradation by iodine extraction under illumination with increasing interlayer distance, suggesting faster degradation. These results provide valuable criteria for selecting 2D perovskites for surface passivation applications aimed at enhancing perovskite stability.

This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea Government (MIST: 2022R1A2C1091017).

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