Slow energy transfer in self-doped beta-conformation film of steric polydiarylfluorenes toward stable dual deep-blue amplified spontaneous emission

Journal article

Exciton behavior is crucial for improving the optoelectronic property of a light-emitting conjugated polymer. Herein, the photoexcitation dynamics of exciton migration and energy transfer in a self-doped β-conformation film of the polydiarylfluorenes (poly[4-(octyloxy)-9,9-diphenylfluoren-2,7-diyl]-co-[5-(octyloxy)-9,9- diphenylfluoren-2,7-diyl], PODPF) are demonstrated. Compared to the first generation of the β-conformation polyfluorene, poly(9,9-dioctylfluorene) (PFO), energy transfer occurs in PODPF β-conformation films in a time period of ≈150 ps, much longer than those of the PFO ones (<5 ps), associated with the effective intrachain energy transfer (few hundred picoseconds), rather than interchain Förster energy transfer (a few picoseconds). Similar to PFO, the PODPF β-conformation also displays well-resolved vibronic emission peaks at 20 K, attributed to the planar and rigid conformation. Interestingly, a residual 0-0 band emission of nonplanar conformation chain segments (435 nm, 2.85 eV) at 20 K also further confirms the exciton migration from the amorphous state to the β-conformation domain in PODPF films. Therefore, the stable dual amplified spontaneous emission (ASE) behavior of the PODPF self-doped films at 461 nm (2.69 eV) and 483 nm (2.57 eV), originates from the individual amorphous and β-conformation domains.

Authors: Xu, M; Sun, L; Wang, S; Lin, J; Yu, M

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Wiley
• Journal: Advanced Optical Materials
• Volume: 10
• Issue: 1
• Article number: 2100723
• Publication date: 2021-10-18
• Acceptance date: 2021-07-14
• DOI: 10.1002/adom.202100723
• EISSN: 2195-1071
• Language: English
• Keywords: polydiarylfluorenes; time-resolved PL spectroscopy; dual amplified spontaneous emission; FFR; energy transfer; beta-conformation