Solution-Processed Electroluminescent Device Based On Soluble TADF Material

Thermally activated delayed fluorescence(TADF)materials have attracted great attention as the third-generation OLED materials in recent years because of potentially high internal quantum efficiency of 100%for the molecules without employing any heavy metals.TADF materials have a small energy gap(△EST)between their S1 and T1 which enables efficient reverse intersystem crossing(RISC)from T1 to S1 and transition to So ground state resulting fluorescent emission.In this way,all singlet and triplet excitons can be converted to photons for light emission,making 100%internal efficiency possible,and overcome the drawback of low efficiency in the first generation of fluorescent materials and the usage of metal in second generation phosphorescent materials.Generally,there are two approaches in fabricating organic light-emitting diode(OLED)or quantum dot based light-emitting diode(QLED)devices:thermal evaporation under vacuum or solution process.Compared with the vacuum deposition,solution processing technology is considered to be an important way to achieve large display and large-scale production,due to its advantage in low-cost,simple process,and large size fabrication.This dissertation studies the soluble TADF materials in solution processed,OLED and QLED.First,study was on the effect of different hole-transport layers(HTL)on the performance of solution-processed non-doped OLED devices based on soluble dendrimer TADF materials.It was found that HTL is beneficial to the carrier transport balance and the improvement of device performance.The second study was on the effects of different HTL,electron transport layer(ETL)and EML thickness on device performance soluble non-doped blue TADF-OLED devices,based on a classic blue TADF material DMAC-DPS as the light emitting layer(EML).By optimizing the device structure,a soluble non-doped TADF-OLED device with low turn-on voltage and high efficiency was prepared.Final study was on the effect of TADF on QLED devices.It was found that the QLED device performances have been improved because the TADF materials improved the hole transport rate and balanced the carriers in QLED devices,and the RISC process in TADF materials improved the exciton utilization bytransfering their energy into the adjacent QDs through Forster resonant energy transfer(FRET).