Chemical Behavior and Local Structure of the Ruddlesden–Popper and Dion–Jacobson Alloyed Pb/Sn Bromide 2D Perovskites
Bibliographic record
Abstract
The alloyed lead/tin (Pb/Sn) halide perovskites have gained significant attention in the development of tandem solar cells and other optoelectronic devices due to their widely tunable absorption edge. To gain a better understanding of the intriguing properties of Pb/Sn perovskites, such as their anomalous bandgap’s dependence on stoichiometry, it is important to deepen the understanding of their chemical behavior and local structure. Herein, we investigate a series of two-dimensional Ruddlesden–Popper (RP) and Dion–Jacobson (DJ) phase alloyed Pb/Sn bromide perovskites using butylammonium (BA) and 3-(aminomethyl)pyridinium (3AMPY) as the spacer cations: (BA) 2 (MA) n −1 Pb x Sn n – x Br 3 n +1 ( n = 1–3) and (3AMPY)(MA) n −1 Pb x Sn n – x Br 3 n +1 ( n = 1–3) through a solution-based approach. Our results show that the ratio and site preference of Pb/Sn atoms are influenced by the layer thickness ( n ) and spacer cations (A′), as determined by single-crystal X-ray diffraction. Solid-state 1 H, 119 Sn, and 207 Pb NMR spectroscopy analysis shows that the Pb atoms prefer the outer layers in n = 3 members: (BA) 2 (MA)Pb x Sn n – x Br 10 and (3AMPY)(MA)Pb x Sn n – x Br 10 . Layered 2D DJ alloyed Pb/Sn bromide perovskites (3AMPY)(MA) n −1 Pb x Sn n – x Br 3 n +1 ( n = 1–3) demonstrate much narrower optical band gaps, lower energy PL emission peaks, and longer carrier lifetimes compared to those of RP analogs. Density functional theory calculations suggest that Pb-rich alloys (Pb:Sn ∼4:1) for n = 1 compounds are thermodynamically favored over 50:50 (Pb:Sn ∼1:1) compositions. From grazing-incidence wide-angle X-ray scattering (GIWAXS), we see that films in the RP phase orient parallel to the substrate, whereas for DJ cases, random orientations are observed relative to the substrate.
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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 | 0.001 |
| 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".