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Simultaneously Enhancing Photoluminescence Quantum Efficiency and Optical Gain of Polyfluorene via Backbone Intercalation of 2,5‐Dimethyl‐1,4‐Phenylene
Author(s) -
Zhang Qi,
Wu Yinan,
Lian Shaoshan,
Gao Jinxin,
Zhang Sihao,
Hai Gang,
Sun Chen,
Li Xiangchun,
Xia Ruidong,
CabanillasGonzalez Juan,
Mo Yueqi
Publication year - 2020
Publication title -
advanced optical materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.89
H-Index - 91
ISSN - 2195-1071
DOI - 10.1002/adom.202000187
Subject(s) - materials science , photoluminescence , polyfluorene , quantum efficiency , fluorene , optoelectronics , polymer , amplified spontaneous emission , absorption (acoustics) , luminescence , laser , quantum yield , conjugated system , optics , fluorescence , composite material , physics
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.