Rare-Earth Substitution of La<sub>3</sub>Si<sub>2</sub>S<sub>8</sub>I for Efficient and Color-Tunable Phosphor Converted White Light Emitting Diodes
Bibliographic record
Abstract
Mixed-anion compounds enable properties to be controlled to a greater degree by chemical substitution than single-anion compounds. La 3 Si 2 S 8 I was investigated as a host to develop phosphors based on solid solutions (La 1– x RE x ) 3 Si 2 S 8 I ( RE = Ce, Pr, Tb, Dy, Ho; x = 0–0.33) and (La 1– x – y Ce x RE y ) 3 Si 2 S 8 I ( RE = Tb, Dy; x, y = 0–0.33) that exhibit wide color tunability and white emission. Upon excitation with a 364 nm UV laser source, the phosphors emit through a down-conversion process over a wide visible color gamut. Depending on the RE 3+ concentration, the spectra featured broad emission (cyan for Ce 3+ ) or sharp 4f–4f emission peaks (red for Ho 3+; green for Tb 3+; cyan-green and red for Pr 3+; yellow and cyan for Dy 3+ ) which can be fine-tuned to a wider gamut. The cosubstituted (La 1– x – y Ce x RE y ) 3 Si 2 S 8 I phosphors showed even more intense photoluminescence and wider color palettes within the cyan to green regions (Ce 3+ –Tb 3+ ) and cool to warm white (Ce 3+ –Dy 3+ ). The photometric parameters were appropriate for backlighting display and near UV-pumped phosphor-converted white light-emitting diodes (pc-wLEDs). Photoluminescence decay profiles follow biexponential behavior with lifetimes ranging from a few ns (for Ce 3+ ) to 3–450 μs (for other RE 3+ ). Most of the optimized phosphors were moderately stable at 80–100 °C before the onset of thermal quenching effects. They gave absolute quantum yields up to 50%, which are favorable for efficient energy conversion. Prototype pc-wLEDs fabricated from a blend of three phosphors or from single-phase phosphors showed promising performance.
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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) | 0.001 | 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".