Narrow‐Linewidth Emission and Weak Exciton‐Phonon Coupling in 2D Layered Germanium Halide Perovskites
Bibliographic record
Abstract
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) 2 GeI 4 and (4F‐PMA) 2 PbI 4 (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) 2 PbI 4 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) 2 GeI 4 , 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.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".