The tunable control in the inorganic octahedral framework of hybrid perovskites offers potential applications in photovoltaics, solid-state lighting, and radiation detection.

However, the implication of the structure and optoelectronic properties pose challenges due to competition between organic–inorganic coupling and intraoctahedral interactions. In this study, we combine X-ray absorption spectroscopy (XAS) and Raman analysis to interpret the angular-dependent behavior and anharmonicity of manganese-based single-crystal perovskites differing by a single methylene unit. The XAS spectra of manganese-based single-crystal perovskites with 2-phenethylamine (PEA) compared to 3-phenyl-1-propylamine (PPA) as organic cations unambiguously demonstrated a 180° intensity shift as a function of the incoming photon, suggesting a pronounced structural ligand variation. The out-of-plane polarization is found to be more prominent in L2-edge than in L3. In addition, an accompanying shoulder peak around 643 eV was attributed to the electron excitation from Mn 2p to 3d orbitals to form d5L states. A decrease in terms of field strength is prominently observed that infers a low crystal field splitting energy. Raman analysis of the two hybrid perovskites displays a notable difference in the respective translational modes at 84 and 87 cm–1, which signifies the amplified anharmonicity due to extended chain length. Based on this phenomenological approach, a longer chain promotes a rather unique octahedral deformation than anharmonicity shift that is crucially important to decoupling the nature of the active units. This effort sheds some light to implement the orientational ordering toward an efficient charge transport of hybrid perovskite semiconductors.

Source: Journal of Physical Chemistry C, 126, 15801-15808 (2022)