Simultaneously Enhancing Photoluminescence Quantum Efficiency and Optical Gain of Polyfluorene via Backbone Intercalation of 2, 5‐Dimethyl‐1, 4‐Phenylene. Issue 12 (30th April 2020)

• Record Type: Journal Article
• Authors: Zhang, Qi; Wu, Yinan; Lian, Shaoshan; Gao, Jinxin; Zhang, Sihao; Hai, Gang; Sun, Chen; Li, Xiangchun; Xia, Ruidong; Cabanillas‐Gonzalez, Juan; Mo, Yueqi
• Is Part Of: Advanced optical materials. Volume 8:Issue 12(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-04-30
• Subjects: 2, 5‐dimethyl‐1, 4‐phenylene -- conjugated polymers -- distributed feedback laser -- optical gain -- polyfluorene; Optical materials -- Periodicals; Photonics -- Periodicals; 620.11295
• DOI: 10.1002/adom.202000187
• Languages: English
• ISSNs: 2195-1071

Abstract

Abstract: 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. Abstract : 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.