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A series of novel hyperbranched polymers(HBPs) consisting of a 2,7-subsituted 9-(heptadecan-9-yl)-9H-carbazole unit(A_2+A_2’) and a tetra-substituted green thermally activated delayed fluorescence(TADF) dye of 2,3,5,6-tetra(9Hcarbazol-9-yl)-4-pyridinecarbonitrile(4CzCNPy, B4) have been synthesized via Suzuki cross-coupling reaction following an “A2+A2’+B_4” method. The polymers are named according to the polymerization ratio of 4CzCNPy monomer(5 mol%, 10 mol% and 15 mol% for HBPs of P2-P4 respectively, and 0 mol% for the control linear polymer P1). Their thermal, optoelectronic and electrochemical properties have been characterized by a combination of techniques. All the polymers exhibit high thermal stability with the decomposition temperatures(Td) above 400 ℃ and glass transition temperatures(Tg) up to 98 ℃. Unfortunately, the incorporation of TADF moiety into these HBP materials induced non-TADF characteristics. However, when the HBPs functionalized as the host for our previously developed 4CzCNPy TADF dopant in solution processed devices, maximum external quantum efficiency of 5.7% and current efficiency of 17.9 cd/A have been achieved in P3-based device, which is significantly higher than those of 1.5% and 4.2 cd/A for the linear polymer P1.
A series of novel hyperbranched polymers (HBPs) consisting of a 2,7-subsituted 9- (heptadecan-9-yl) -9H-carbazole unit (A_2 + A_2 ’) and a tetra-substituted green thermally activated delayed fluorescence (TADF) dye of 2,3,4,6-tetra (9Hcarbazol-9-yl) -4-pyridinecarbonitrile (4CzCNPy, B4) have been synthesized via Suzuki cross-coupling reaction following an “A2 + A2 ’+ B_4” method. The polymers were identified according to the polymerization ratio of 4CzCNPy monomer (5 mol%, 10 mol% and 15 mol% for HBPs of P2-P4 respectively, and 0 mol% for the control linear polymer P1). Their thermal, optoelectronic and electrochemical properties have been characterized by a combination of techniques. All the polymers exhibit high thermal stability with the decomposition temperatures (Td) above 400 ° C and glass transition temperatures (Tg) up to 98 ° C. Unfortunately, the incorporation of TADF moieties into these HBP materials induced non-TADF characteristics. However, when the HBPs functionalized as the host for our previou sly developed 4CzCNPy TADF dopant in solution processed devices, maximum external quantum efficiency of 5.7% and current efficiency of 17.9 cd / A have been achieved in P3-based device, which is significantly higher than those of 1.5% and 4.2 cd / A for the linear polymer P1.