Novel Fluorene-Based Copolymers Containing Branched 2-Methyl-butyl-Substituted Fluorene-co-benzothiadiazole Units for Remarkable Optical Gain Enhancement in Green-Yellow Emission Range

作者：Yu, Zhou; Guo, Xiangru; Zhang, Qi; Chi, Lang; Chen, Ting; Xia, Ruidong^*; Wu, Longfei; Luer, Larry; Cabanillas-Gonzalez, Juan^*

来源：Journal of Physical Chemistry C, 2016, 120(21): 11350-11358.

DOI：10.1021/acs.jpcc.6b01375

• AMPLIFIED SPONTANEOUS EMISSION
• EXCITON-EXCITON ANNIHILATION
• CONJUGATED-POLYMER
• MEH-PPV
• CHARGE-TRANSPORT
• ULTRAFAST
• POLYFLUORENE
• DIFFUSION
• FILMS
• PHOTOEXCITATION

We develop novel fluorene-based green-yellow emission copolymers (namely, nF1/4F8BT) composed of poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT) and branched 2-methyl-butyl substituted fluorene-co-benzothiadiazole units (Ft/4BT) in different ratios. Upon blending nF1/4F8BT copolymers with poly(9,9-dioctylfluorene) (PFO), a systematic increase in photoluminescence quantum efficiency is observed as the ratio of the branched monomers increase. Likewise, nF1/4F8BT and PFO:nF1/4F8BT blends exhibit superior optical gain properties with respect to F8BT, manifested as a 30% reduction of amplified spontaneous emission threshold and 50% increase in optical gain with respect to F8BT blends at the same emission wavelength. The optical-gain-related properties were studied to understand the influence of the branched side chain unit on stimulated emission properties. Femtosecond transient absorption studies confirm exciton-annihilation hindrance in the new copolymers likely caused by interference of branched substituents with molecular packing in films. Branch side-chain substitution of a limited number of monomers is an efficient strategy to boost the optical gain properties of conjugated polymers.

• 出版日期2016-6-2
• 单位南京邮电大学