Narrow-Linewidth Emission and Weak Exciton-Phonon Coupling in 2D Layered Germanium Halide Perovskites.
basic_science · Level V
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- Record sourced from PubMed, PMID 40290086.
- Also identified by DOI 10.1002/adma.202419879.
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Abstract
The photophysical properties of low-dimensional metal-halide semiconductors and their tunability make them promising candidates for light-absorbing and emitting applications. Yet, the germanium-based halide perovskites to date lack desirable light-emitting properties, with so far only very broad, weak, and unstructured photoluminescence (PL) reported due to significant octahedral distortion. Here, the photophysical properties of the 2D layered Ruddlesden-Popper semiconductors (4F-PMA)<sub>2</sub>GeI<sub>4</sub> and (4F-PMA)<sub>2</sub>PbI<sub>4</sub> (4F-PMA: 4-F-phenylmethylammonium) are characterized and compared. Using a combination of single-crystal X-ray diffraction, variable temperature time-resolved PL, and density functional theory, structure-property relations are correlated. Specifically, the results indicate that (4F-PMA)<sub>2</sub>PbI<sub>4</sub> features stronger coupling to longitudinal optical (LO) phonons, assisting emission from a broad bound-exciton state due to a soft, deformable lattice. In contrast, (4F-PMA)<sub>2</sub>GeI<sub>4</sub>, benefitting from intermolecular bonding to scaffold a rigid octahedral structure, shows weaker LO-phonon coupling, resulting in the longest PL lifetime and most narrow linewidth (≈120 meV linewidth at 2 K) reported for a Ge-halide perovskite yet, without the occurrence of any additional bound-state emission at low temperatures. These results highlight the potential of germanium halide perovskite materials for optoelectronic applications.