Jin Su Park

Novel fluorene-based functional ‘click polymers’ for quasi-solid-state dye-sensitized solar cells

Quasi-solid-state DSSCs in SnO(2):F/quasi-solid-state electrolyte/Pt devices have been fabricated with click polymers for the first time; they show a maximum power conversion efficiency (PCE) of 2.80%.

Synthesis and Characterization of Spirobifluorene-Based Polymers for Organic Light-Emitting Diode Applications

The following series of blue EL polymers was synthesized using the Suzuki polymerization method: poly(3′,6′-bis(3,7-dimethyloctyloxy)-9,9′-spirobifluorene-2,7-diyl) poly[(OC10)2-spirobifluorene], poly(3′,6′-bis(3,7-dimethyloctyloxy)-9,9′-2,7-diyl-co-4-(3,7-dimethyloctyloxy) phenyl-diphenylamine-4′,4′-diyl} poly[(OC10)2-spirobifluorene-TPA] (5∶1, 9∶1) and poly(3′,6′-bis(3,7-dimethyloctyloxy)-9′,9′-spirobifluorene-2,7-diyl-co-4-(6-((3-methyloxetan-3-yl)methoxy) hexyloxyphenyl-bisphenylamine-4′,4′-diyl) poly[(OC10)2-spirobifluorene-TPA-oxetane]. The weight average molecular weight (Mw) and polydispersity of the resulting polymers ranged from 1.6×104–1.5×105 and 1.77–2.31, respectively. The resulting polymers were completely soluble in common organic solvents and were easily spin-coated onto an indium tin oxide (ITO) substrate. The polymers exhibited strong blue emission peaking at 450 nm. The maximum brightness and luminance efficiency were 9,960 cd/m2 and 1.2 cd/A, respectively.

Green phosphorescent light-emitting diodes from polymer doped with iridium complex

We demonstrate efficient organic light-emitting diodes by using a phosphorescent host/guest system consisting of a recently developed green electrophosphorescent molecule, bis[(4,6-difluorophenyl)-8-methylpyridinato-N,C2′)iridium pyrazinate [(dfmppy)2Irprz], as the guest and a blend of poly(N-vinylcarbazole) (PVK) with 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD) as the host and different cathode structures such as a triple layer of BAlq∕LiF∕Al and a bilayer of CsF∕Al. The electrophosphorescence emission was characteristic of (dfmppy)2Irprz, with its maximum at 563nm with Commission International de L’Eclairage coordinates of (0.43, 0.53). The device with 0.5wt% of (dfmppy)2Irprz in PVK/PBD (60:40wt%) with a CsF (2nm)∕Al bilayer exhibited an external quantum efficiency of 6.2%, luminescence efficiency of 17.3cd∕A, luminous power efficiency of 24.2lm∕W, and maximum brightness of 10220cd∕m2.

Synthesis and Electro-Optical Properties of Fluorene-Based Copolymer for Organic Photovoltaic Device Application

The following soluble π-conjugated polymer was synthesized by palladium-catalyzed Suzuki polymerization: poly[(9,9-dioctylfluorene)-alt-(3-hexylthiophen-5-yl)-(4′-hexylthiazol-5′-yl)] poly(FO-HThHTha) derived from poly(9,9-dioctylfluorene) (PFO) and poly[(3-hexylthiophen-5-yl)-2,2′-(4′-hexylthiazol-5′-yl)] poly(HThHTa). The polymer, poly(FO-HThHTa) was soluble in common organic solvents and easily spin coated onto indium-tin oxide (ITO) coated glass substrates. Bulk heterojunction photovoltaic cells with an ITO/PEDOT/poly(FO-HThHTa):PC70BM/TiOx/Al configuration were fabricated and the photovoltaic cell using poly(FO-HThHTa):PC70BM (1:4) showed the best photovoltaic performance compared with those using poly(FO-HThHTa):PC70BM (1:2 and 1:6). The optimal bulk heterojunction photovoltaic cell exhibits a power conversion efficiency (PCE) of 0.39% (Voc = 0.44 V, Jsc = 2.57, FF = 0.34) with poly(FO-HThHTa):PC70BM (1:4) measured by using an AM 1.5 G irradiation (100 mW/cm2) on an Oriel Xenon solar simulator (Oriel 300 W).

Synthesis and Characterization of Carbazole-based Copolymers Containing Benzothiadiazole Derivative for Polymer Light-Emitting Diodes

A new thermally robust electroluminescent (EL) carbazole-based π-conjugated copolymer, including poly[3,7-(N-hexylcarbazole)-co-4,7-{5,6-bis(3,7-dimethyloctylo- xymethyl)-2,1,3-(benzothiadiazole)}] (PCz- co -P2C10BT) was synthesized and used to fabricate the efficient polymer light-emitting diodes (PLEDs). The glass transition temperature of the PCz- co -P2C10BT (105°C) was found to be higher than that of poly(9,9-dialkylfluorene) derivatives. We fabricated PLEDs in ITO/PEDOT/light-emitting polymer/Alq3/LiF/Al configuration. The new copolymer was found to have green emission color (523 nm). The maximum brightness and external quantum efficiency of PCz- co -P2C10BT were 260 cd/m2 at 14 V and 0.22%, respectively.