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.