Study And Industrial Synthesis Of High Efficiency Blue Fluorescent Materials Based On Anthracene

Organic light emitting diode（OLED）has attracted much attention in the field of lighting and displaying because of its advantages,such as low turn-on voltage,wide viewing angle,self-luminous,ultra-thin,and flexibility.The performances of OLED are usually dependent on the properties of the organic light-emitting materials,as the core of OLED.However,the limit of exciton utilization efficiency（EUE）for the traditional fluorescent small molecule materials is only 25%because of spin-forbidden transition,and results in the maximum external quantum efficiency（EQE）of OLED of 5%.Therefore,it is an important challenge to design molecule with a EUE beyond 25%in fluorescent materials.Hybridized local and charge-transfer（HLCT）is a new type of emitting materials with high EUE.By adjusting the locally excited electron（LE）and charge transfer（CT）state,the theoretical EUE limit of traditional fluorescent materials could be broken,consequently,high efficiency OLED can be obtained.In addition,to realize the commercialization of emitting materials,the synthesis and purification with high yield are also extremely important.To resolve above problems,the novel blue fluorescent materials were designed and synthesized.As follows:（1）The blue fluorescent materials with D-π-A structure were designed and synthesized using anthracene asπ-conjugated group,carbazole（Cz）as donor（D）and triazine（A）as acceptor（A）groups,namely 3-（10-（3-（4,6-diphenyl-1,3,5-triazin-2-yl）phenyl）anthracene-9-yl）-9-phenyl-9h-carbazole（m-TAC）and 3-（10-（4-（4,6-diphenyl-1,3,5-triazin-2-yl）phenyl）anthracene-9-yl）-9-phenyl-9h-carbazole（p-TAC）,which anthracene were introduced on the inter-and para-positions of triazine.Their thermal stabilities,photophysical properties,excited state and performance in OLED were investigated.The results indicated that the maximum emission peaks in the thin film of m-TAC and p-TAC were located at 431 and462 nm.The compound of p-TAC exhibited HLCT excited state.The non-doped blue OLED were fabricated using m-TAC and p-TAC as light-emitting materials.The device based on p-TAC displayed the better performances with the maximum emission peak at 476 nm,CIE（commission International de L′Eclairage,CIE）of（0.18,0.30）,the maximum external quantum efficiency（EQE）of 5.03%and EUE of 76.79%,exceeding the theoretical limit value for conventional fluorescent devices.The devices present excellent stability with the value of 1.4%efficiency roll-off at 1000 cd m^-2.（2）To avoid the aggregate in film,triphenylamine was chosen as D group due to its right steric hindrance and enteron donating ability,anthracene as theπ-conjugated group,triazine as the A group to design blue fluorescent materials with D-π-A structures,namely,4-（10-（3-（4,6-diphenyl-1,3,5-triazin-2-yl）phenyl）anthracene-9-yl）-N,N-diphenylamine（m-TAT）and 4-（10-（4-（4,6-diphenyl-1,3,5-triazin-2-yl）phenyl）anthracene-9-yl）-N,N-diphenylamine（p-TAT）,Their thermal stabilities,photophysical properties,the natures of excited state and performance in OLEDs were investigated in detail.The results showed that the maximum emission peaks in the thin film of m-TAT and p-TAT were located at 483 and 491 nm,which were in the sky-blue range.The compound of p-TAT exhibited HLCT excited state.The non-doped blue OLED were fabricated using m-TAT and p-TAT as light-emitting materials.The device based on p-TAT displayed the better performances than that of other ones with the maximum emission peak at 488 nm,the color coordinate is（0.18,0.37）,the maximum EQE of 5%,and EUE of37.03%.（3）The molecule of p-TAC was selected to investigate the commercial application due to its performances superior to others.Since the anthracene derivatives possess the poorly solubility,it is difficult to obtain materials with a purity of 99.99%by column chromatography.Thus,each reaction step was checked by liquid chromatography（HPLC）to ensure a high purity of intermediates over 99.5%.The final product was sublimated to achieve a purity of above99.9%to meet the requirements of industrial device preparation.