New low band gap thieno[3,4-b]thiophene-based polymers with deep HOMO levels for organic solar cells
Bibliographic record
Abstract
Two new soluble alternating alkyl-substituted benzo[1,2-b:4,5-b′]dithiophene and ketone-substituted thieno[3,4-b]thiophene copolymers were synthesized and characterized. We found that grafting 3-butyloctyl side chains to the benzo[1,2-b:4,5-b′]dithiophene unit at C4 and C8 afforded the resulting polymer (P1) a high hole mobility (∼10−2 cm2Vs−1) and a low-lying HOMO energy level (5.22 eV). Preliminary experiments in bulk heterojunction solar cells using P1 as the electron donor demonstrated a high power conversion efficiency of 4.8% even with PC61BM as the electron acceptor. The introduction of an electron-withdrawing fluorine atom into the thieno[3,4-b]thiophene unit at the C3 position (P2) lowers the HOMO energy level and consequently improves the open circuit voltage from 0.78 to 0.86 V. These values are about 0.1 V higher than those reported for their analogues based on alkoxy-substituted benzo[1,2-b:4,5-b′]dithiophene. This work demonstrates that the replacement of the alkoxy chains on the benzo[1,2-b:4,5-b′]dithiophene unit with less electron-donating alkyl chains is able to lower the HOMO energy levels of this class of polymers without increasing their band gap energy.
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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 | 0.001 |
| 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".