Synthsis And Properties Of Bipolar Materials For Blue Phosphorescent Organic Light-emitting Diodes

Four series of six kinds novel bipolar blue phosphorescent organic light-emitting diodes(PhOLED), containing hole-transporting moieties,such as carbazole structure,phenothiazine structure and triphenylamine structure and electron- transporting moieties,such as benzoimidazole structure, triazine structure, 3-Bromobenzonitrile structure and1,2,4-oxadiazole structure, were designed and synthesized in this thesis. They were characterized by means of 1H NMR, 13 C NMR,and elemental analysis. The optical,electrochemical and thermal properties were also investigated.1.Bipolar blue PhOLED host materials containing benzoimidazole derivatives structureUsing carbazole, N-Phenyl-o-phenylenediamine and 4-Fluorobenzoyl chloride as raw materials, We have designed and synthesized a novel benzoimidazole derivatives,1-phenyl-2-[4-(N- carbazol-9-yl) phenyl] benzoimidazole(PCPB), as bipolar host materials for blue PhOLED.The results show that the maximum absorption wavelengths of PCPB are located at about 296, 368 nm in dilute CH2Cl2 solution. PCPB can emit navy blue fluorescence at 401 nm in dilute CH2Cl2 solution,and exhibit blue phosphorescent emission at 452 nm from the highest-energy vibronic subband at 77 K, from which its triplet state energy(ET) is estimated to be 2.74 eV.PCPB can be used as host material for the blue emitter bis(4,6-difluorophenylpyridine)(picolinate)(Ⅲ)(Firpic) in PhOLED. DFT theoretical calculation reveals that the highest occupied molecular orbital(HOMO) of PCPB is mainly distributed on N-phenly carzole moiety, while the lowest unoccupied molecular orbital(LUMO) is mainly dispersed over the benzoimidazole moiety. Cyclic voltammetry measurement shows that HOMO energy level of PCPB is located at-5.54 eV, which match with the energy levels of ITO(-4.5~-5.0 eV); LUMO energy level of PCPB is located at-2.68 eV, which is close to the energy level of PBD(-2.82 eV). So PCPB possess bipolar properties of hole and electron transport and good thermal stability.2.Bipolar blue PhOLED host materials containing triazine derivatives structureWith carbazole, Cyanuric chloride and 1-Naphthol as raw materials, We have designed and synthesized a novel triazine derivatives, 9-(4-(4,6-di-α-naphthoxy-1,3,5-triazin-2-yl) phenyl) carbazole(NOTPC), as bipolar host materials for blue PhOLED. The results show that the maximum absorption wavelengths of NOTPC are located at about 290, 340 nm in dilute CH2Cl2 solution. NOTPC can emit blue photofluorescence at 390, 472 nm in dilute CH2Cl2 solution, and exhibit bluephosphorescent emission at 452 nm from the highest-energy vibronic subband at 77 K,from which its triplet state energy(ET) is estimated to be 2.80 eV. NOTPC can be used as host material for the blue emitter Firpic in PhOLED. DFT theoretical calculation reveals that the HOMO of NOTPC is mainly distributed on N-phenly carzole moiety, while the LUMO is mainly dispersed over the triazine moiety. Cyclic voltammetry measurement shows that HOMO energy level of PCPB is located at-5.40 eV, which match with the energy levels of ITO(-4.5~-5.0 eV); LUMO energy level of PCPB is located in-2.32 eV, which is close to the energy level of PBD(-2.82eV). So NOTPC possess bipolar properties of hole and electron transport and good thermal stability.3. Bipolar blue PhOLED host materials containing phenothiazine derivatives structureUsing phenothiazine, 3-Bromobenzonitrile as raw materials, We have designed and synthesized a novel 3-Bromo- benzonitrile derivatives, 3,3′-(9H,9′H-[3,3′-bi phenothiazine]-9,9′-diyl)dibenzonitrile(3CN33BPTZ), as bipolar host materials for blue PhOLED. The results show that the maximum absorption wavelengths are located at about 262, 306 nm in dilute CH2Cl2 solution. 3CN33 BPTZ can emit navy blue photofluorescence at 410 nm in dilute CH2Cl2 solution, and exhibits blue phosphorescent emission at 423 nm from the highest-energy vibronic subband at 77 K,from which its triplet state energy(ET) is estimated to be 2.93 eV. 3CN33 BPTZ can be used as host material for the blue emitter Firpic in PhOLED. DFT theoretical calculation reveals that the HOMO of 3CN33 BPTZ is mainly distributed on phenothiazine moiety, while LUMO is mainly dispersed over the 3-Bromobenzonitrile moiety. Cyclic voltammetry measurement shows that HOMO energy level of3CN33 BPTZ is located in-5.92 eV, which match with the energy levels of ITO(-4.5~-5.0 eV); LUMO energy level of 3CN33 BPTZ is located in-2.79 eV,which is close to the energy level of PBD(-2.82 eV). So 3CN33 BPTZ possess bipolar properties of hole and electron transport, and good thermal stability.4. Bipolar blue PHOLED host materials containing 1,2,4-oxadiazole derivatives structureWith carbazole, phenothiazine and 4-Bromobenzonitrile as raw materials, We have designed and synthesized three novel 1,2,4-oxadiazole derivatives, 3,5-bis(4-diphenylaminophenyl)-1,2,4-oxadiazole(BAOXD), 3,5-bis(4-(9H- phenol- thiazine-9-yl)phenyl)-1,2,4-ox adiazole(PPOXD) and 3,5-bis(3-(9H- phenol- thiazine-9-yl)phenyl)-1,2,4-oxadi azole(MMOXD), as bipolar host materials for blue PhOLED.Those triplet state energy(ET) are estimated to be 2.77, 2.46 and 2.93 eV. BAOXD and MMOXD can be used as host material for the blue emitter Firpic in PhOLED.However, PPOXD can meet the basic requirement of green phosphorescence host material for the green emitter fac-tris(2-phenylpyridine) iridium Ir(ppy)3(>2.40 eV) in PhOLED. Cyclic voltammetry measurement shows that HOMO energy level of BAOXD, PPOXD and MMOXD are located in-5.70、-5.25 and-5.88 eV, which match with the energy levels of ITO(-4.5 ~-5.0 eV); LUMO energy level of BAOXD、PPOXD and MMOXD are located in-2.30、-2.32 and-2.64 eV, which is close to the energy level of PBD(-2.82 eV). So BAOXD、PPOXD and MMOXD possess bipolar properties of hole and electron transport and good thermal stability.