Hydrogen Disproportionation Reduces the Bandgap and Prolongs the Carrier Lifetime in Cs <sub>2</sub> AgBiBr <sub>6</sub> : Quantum Dynamics Analysis
Bibliographic record
Abstract
Cs 2 AgBiBr 6 is a promising lead-free double perovskite with excellent stability, but it suffers from a large bandgap for optoelectronic applications. Hydrogenation is reported not only to reduce the bandgap but also to prolong the carrier lifetime in Cs 2 AgBiBr 6, improving device efficiencies significantly. In order to elucidate the mechanisms underlying these phenomena, we combine density functional theory and nonadiabatic molecular dynamics and reveal the role of hydrogen (H) atoms in Cs 2 AgBiBr 6 . We demonstrate that H atoms spontaneously undergo a disproportionation reaction to form H + and H – . The H – anions form chemical bonds with the Bi 3+ cations and introduce midgap states to reduce the bandgap, with the calculated bandgap change comparable to the experimental observation. Moreover, these states facilitate electron–hole separation in Cs 2 AgBiBr 6, suppressing their recombination and, thus, extending the carrier lifetime, despite the reduced bandgap. Our results rationalize the experimental phenomena and provide crucial insights into the development of novel lead-free perovskite materials.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| 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) | 0.003 | 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 source (direct Gemma or distilled Codex), 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".