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F8BT Oligomers for Organic Solid-State Lasers.
Masashi Mamada1,2,3, Ryutaro Komatsu1,2,4, Chihaya Adachi1,2,3,5
1Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, Fukuoka 819-0395, Japan.
ACS Applied Materials & Interfaces
|May 27, 2020
Summary
Researchers developed high-purity oligomers of poly(9,9-dioctylfluorene-alt-benzothiadiazole) (F8BT) to overcome polymer inconsistencies. These oligomers exhibit superior photoluminescence quantum yields and lower amplified spontaneous emission thresholds, showing promise for light-emitting devices.
Area of Science:
- Organic electronics
- Polymer science
- Materials chemistry
Background:
- Poly(9,9-dioctylfluorene-alt-benzothiadiazole) (F8BT) is a versatile yellow-green emissive polymer.
- F8BT exhibits significant performance variations due to purity, polydispersity, and reproducibility issues.
- Existing F8BT polymers show a wide range of photoluminescence quantum yields (PLQYs) from 7% to 60%.
Purpose of the Study:
- To address the performance inconsistencies of F8BT polymers.
- To synthesize and investigate F8BT oligomers as a high-purity alternative.
- To evaluate the optical and electronic properties of F8BT oligomers compared to the polymer.
Main Methods:
- Synthesis of three F8BT oligomers (M1-M3).
- Measurement of photoluminescence quantum yields (PLQYs) in neat films.
- Determination of amplified spontaneous emission (ASE) thresholds.
- Characterization of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels.
- Evaluation of ASE in near-infrared laser emitter devices doped with F8BT and oligomer hosts.
Main Results:
- Synthesized F8BT oligomers achieved high purity.
- Oligomers demonstrated significantly higher PLQYs (>80%) compared to conventional F8BT films.
- ASE thresholds for oligomers were lower than F8BT (e.g., 1.9 μJ cm⁻² for M3 vs. 2.7 μJ cm⁻² for F8BT).
- HOMO and LUMO energy levels of oligomers were comparable to F8BT.
- ASE performance showed distinct differences between F8BT and oligomer hosts despite similar steady-state emission.
Conclusions:
- F8BT oligomers offer a high-purity, high-performance alternative to F8BT polymers.
- The improved properties of oligomers stem from higher net gain and better film morphology.
- F8BT oligomers are promising candidate materials for host applications in light-emitting devices.
