The influence of solid‐state microstructure on the origin and yield of long‐lived photogenerated charge in neat semiconducting polymers
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Bibliographic record
Abstract
Abstract The influence of solid‐state microstructure on the optoelectronic properties of conjugated polymers is widely recognized, but still poorly understood. Here, we show how the microstructure of conjugated polymers controls the yield and decay dynamics of long‐lived photogenerated charge in neat films. Poly(3‐hexylthiophene) was used as a model system. By varying the molecular weight, we drive a transition in the polymer microstructure from nonentangled, chain‐extended, paraffinic‐like to entangled, semicrystalline ( M W = 5.5–347 kg/mol). The molecular weight range at which this transition occurs ( M W = 40–50 kg/mol) can be deduced from the drastic change in elongation at break found in tensile tests. Linear absorption measurements of free‐exciton bandwidth and time‐resolved microwave conductivity (TRMC) measurements of transient photoconductance track the concomitant evolution in optoelectronic properties of the polymer as a function of M W . TRMC measurements show that the yield of free photogenerated charge increases with increasing molecular weight in the paraffinic regime and saturates at the transition into the entangled, semicrystalline regime. This transition in carrier yield correlates with a sharp transition in free‐exciton bandwidth and decay dynamics at a similar molecular weight. We propose that the transition in microstructure controls the yield and decay dynamics of long‐lived photogenerated charge. The evolution of a semicrystalline structure with well‐defined interfaces between amorphous and crystalline domains of the polymer is required for spatial separation of the electron and hole. This structural characteristic not only largely controls the yield of free charges, but also serves as a recombination center, where mobile holes encounter a bath of dark electrons resident in the amorphous phase and recombine with quasi first‐order kinetics. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011
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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 | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 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 it