Atomistic Description of the Impact of Spacer Selection on Two-Dimensional (2D) Perovskites: A Case Study of 2D Ruddlesden-Popper CsPbI 3 Analogues.

Inorganic CsPbI 3 perovskites have become desirable for use in photovoltaic devices due to their excellent optoelectronic properties and increased resilience to thermal degradation compared to organic-inorganic perovskites. An effective strategy for improving both the performance and the phase stability of CsPbI 3 -based perovskites is through introducing a diverse set of spacing cations separating inorganic layers in their two-dimensional (2D) analogues. In this work, CsPbI 3 -based 2D Ruddlesden-Popper perovskites were investigated using three aromatic spacers, 2-thiophenemethylamine (ThMA), 2-thiopheneformamidine (ThFA), and benzylammonium, fluorinated through para substitution (pFBA). Our findings highlight the importance of the local bonding environment between organic spacers and the PbI 6 octahedra. Additionally, we demonstrated the importance of energetic alignment between electronic states on spacing cations and inorganic layers for optoelectronic applications. Furthermore, thermoelectric performance was investigated revealing a preference for p-type ThFA and n-type ThMA and pFBA configurations.