Structural and Optoelectronic Investigations of Smallest Organic Spacers Based 2D Ruddlesden-Popper and Dion-Jacobson Perovskites

In recent years, 2D metal halide perovskites (MHPs) emerged as organic-inorganic solution processable semiconductors attributed to their enhanced structural stability and unique optoelectronic properties compared to 3D MHPs [1,2]. The 2D MHPs are mainly classified into two phases named Ruddlesden-Popper (RP) and Dion-Jacobson (DJ) perovskites, which depend on the incorporated organic spacer type and its arrangement [2]. To investigate how the incorporated organic spacer type can affect the fundamental properties and which is better for optoelectronics. In this work, we incorporated the smallest and analogous organic spacers ‘ethylammonium’ (EA) and ‘ethylenediammonium’ (EDA) in MAPbI₃ to form analogous RP-EA and DJ-EDA perovskites (n=1-4), respectively and investigated their structural, morphological, dielectric, and optoelectronic properties [3]. In addition, the effective high-frequency dielectric constants (ε_eff) of RP-EA and DJ-EDA are estimated and correlated with their optical properties, which showed that higher ε_eff mismatch from bulk counterparts (MAPbI₃) is responsible for sharp exciton absorbance behaviour observed in the DJ-EDA perovskite thin films. Furthermore, the DJ-EDA perovskite-based photodetectors revealed improved stability and a higher photoresponsivity of ∼1.00 mA/W (n=4). They retained 97.67% (n=2) of the initial photocurrent after 50 cycles under 1 Sun illumination in the ambient atmosphere conditions owing to their van der Waals gap-free structure. On the other hand, the RP-EA perovskite photodetectors showed fast response times, which is attributed to better band alignment and in-plane crystal morphology. This work provides the fundamental understanding of structural and photophysical properties of the smallest carbon chain organic spacers-based RP and DJ perovskites, which can further their development for several other optoelectronic applications.<br/><br/><b>References:</b><br/>[1] <b>Yadav, A</b>.; Rahil, M.; Ahmad, S. “Facile and Effective Band Gap Engineering of 2D Ruddlesden–Popper Perovskites with Improved Structural and Optoelectronic Properties.” <i>ACS Appl. Electron. Mater.</i> 2023, 5 (2), 1024–1034.<br/>[2] Li, X.; Hoffman, J. M.; Kanatzidis, M. G. “The 2D Halide Perovskite Rulebook: How the Spacer Influences Everything from the Structure to Optoelectronic Device Efficiency.” <i>Chem. Rev.</i> 2021, 121 (4), 2230–2291.<br/>[3] <b>Yadav, A.</b>; Vashist, R.; Rahil, M.; Ren, Z.; Yang, Y.; Zhao, B.; Ahmad, S. “Smallest Organic Spacers based Ruddlesden-Popper and Dion-Jacobson Perovskites: Which one is better for Optoelectronics?” <i>J. Phys. Chem. C</i> 2023, 127, 45, 22190–22203.