Simultaneously Enhancing Photoluminescence Quantum Efficiency and Optical Gain of Polyfluorene via Backbone Intercalation of 2,5‐Dimethyl‐1,4‐Phenylene

Simultaneous enhancement of photoluminescence quantum efficiency (PLQE) and optical gain in semiconducting polymer films is desirable for optically‐ or electrically‐pumped organic solid‐state lasers. In this work, a simple self‐dilution effect is achieved by introducing a small amount (≈10% by weigh...

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Bibliographic Details
Published in:Advanced optical materials 2020-06, Vol.8 (12), p.n/a
Main Authors: Zhang, Qi, Wu, Yinan, Lian, Shaoshan, Gao, Jinxin, Zhang, Sihao, Hai, Gang, Sun, Chen, Li, Xiangchun, Xia, Ruidong, Cabanillas‐Gonzalez, Juan, Mo, Yueqi
Format: Article
Language:English
Subjects:
2,5‐dimethyl‐1,4‐phenylene
Backbone
conjugated polymers
Copolymers
Decay rate
Dilution
distributed feedback laser
Distributed feedback lasers
Materials science
optical gain
Optical properties
Optics
Photoluminescence
polyfluorene
Polymer films
Polymers
Quantum efficiency
Reduction
Spontaneous emission
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Summary:Simultaneous enhancement of photoluminescence quantum efficiency (PLQE) and optical gain in semiconducting polymer films is desirable for optically‐ or electrically‐pumped organic solid‐state lasers. In this work, a simple self‐dilution effect is achieved by introducing a small amount (≈10% by weight) of 2,5‐dimethyl‐1,4‐phenylene (DP) units in the backbone of poly(9,9‐dioctylfluorene) (PFO). The resulting copolymers, compared with PFO (PLQE 39%), exhibit a significantly increased PLQE (66%) while keeping similar absorption and photoluminescence profile, concomitant with an enhancement in optical gain properties. The radiative decay rate increases sharply along with a sustaining reduction in the non‐radiative decay rate in these copolymers, following similar principle of physical dilution of a luminescent compound in solution or in a polymer matrix. Among all the copolymers, the one containing 10% DP units exhibits the lowest amplified spontaneous emission/distributed feedback laser threshold (10.9 nJ/1.4 nJ, eightfold reduction), and the highest gain coefficient (54.4 cm−1). The results demonstrate that a moderate DP/fluorene ratio can maximize the beneficial self‐dilution effects. These investigations shed light on new design strategies to achieve conjugated polymers with concurrent high PLQE and large optical gain properties. By copolymerizing small fractions (≦30% by weight) of 2,5‐dimethyl‐1,4‐phenylene (DP) units with 9,9‐dioctylfluorene (PFO) units, the resulting copolymers show simultaneous enhancement in the photoluminescence quantum efficiency (PLQE) and optical gain. The copolymer containing 10% DP units exhibits an increased PLQE value of 66% (comparing with 39% in PFO) and very low ASE/DFB lasing threshold.
ISSN:2195-1071
2195-1071
DOI:10.1002/adom.202000187