Abstract
In the thesis, high quantum effieiency fluorescent dopants based on stilbene derivatives, PCzDFA、PCzNA、PCzDPA and PCzDMA have been synthesized. In order to increase the solubility and fine tune the emission color, different carbazole or amine groups are incorporated into stilbene structure, all these materials have deep blue emission in dilute toluene solution, and these compounds also exhibit good thermal stability with decomposition temperature in the range of 417~460 °C and glass transition temperature above 100 °C. The HOMO and LUMO levels of these materials are 5.23~5.55 eV and 2.48~2.70 eV, respectively. Moreover, stilbene derivatives doped in DMPPP film show extremely high Q.Y. which indicate that energy transfer is highly efficient. The devices using DMPPP doped with dopants as emission layer (EML) with optimized device structure show extraordinary external quantum efficiency (E.Q.E.). The PCzDPA-doped device shows an E.Q.E. of 9.7 %, the current efficiency (C.E.) of 12.4 cd/A, and the power efficiency (P.E.) of 6.1 lm/W with the CIE coordinates of (0.14, 0.15). The PCzNA-doped device has deeper blue color of CIE coordinates of (0.14, 0.12), and shows an E.Q.E. of 9.4 %, the C.E. of 10.3 cd/A, and the P.E. of 4.9 lm/W. For operation lifetime, the optimized device hosted by m-PPT was fabricated, and using PCzDFA、PCzNA、PCzDPA and PCzDMA as the dopant, the operational lifetime of devices 2J、2K、2L and 2M were 51、91、139 and 148 hours under a luminance of 2000 cd/m2. The poor lifetime may due to the irreversible oxidation. For solution process device, the device 2X using PO-C6 and PCzDPA as host and dopant, respectively, can achieve an E.Q.E. of 4.7 %, the C.E. of 8.4 cd/A, and the P.E. of 6.0 lm/W with the CIE coordinates of (0.15, 0.24). We have synthesized six Styrylpyrene-based derivatives PCzSP、NASP、DFASP、DPASP、DMASP and DOASP as blue fluorescent dopnat materials. Pyrene group, which shows high quantum yield and good thermal property, was proved that can accept triplet exciton then generate additional singlet exction via up-conversion. The photoluminescence of these materials in toluene solution were in blue region. these compounds also exhibit good thermal stability with decomposition temperature in the range of 410~452 °C and glass transition temperature nearly 100 °C. The HOMO and LUMO levels of these materials are 5.16~5.56 eV and 2.37~2.62 eV, their absolute fluorescent quantum yields were measured, DFASP (ΦPL = 0.94) and DPASP (ΦPL = 0.99) exhibit higher ΦPL as compared to PCzSP (ΦPL = 0.64). The devices using DMPPP doped with dopants as EML with optimized device structure show extremely high E.Q.E., the DFASP and DPASP-doped device shows an E.Q.E. of 10.9 and 10.7 %, the C.E. of 11.9 and 13.0 cd/A, the P.E. of 6.1 and 8.9 lm/W with the CIE coordinates of (0.14, 0.14) and (0.14, 0.12), respectively. the devices hosted by CBP was fabricated. The transient EL spectrum of device 3M~3N demonstrated that CBP can not generate TTA, and DPASP doped in CBP show large microsecond-scale delayed fluorescence. The transient PL of dopant and doped-film also eliminate the delay fluorescence which come from TADF(thermally activated delayed fluorescence). The E.Q.E. reached the limit efficiency of fluorescent OLEDs. These results are among of the best performance of deep blue fluorescent OLEDs. For operation lifetime, devices 3Q~3V were 1551、3947、2248、4634、9109 and 3557 hours under a luminance of 500 cd/m2, the better results may due to the reversible oxidation state, except PCzSP. Finally, We have synthesized a series of pyridine-anthracene bsed derivatives p-TPyAP、m-TPyAP、p-TPyAN、and m-TPyAN, the DFT calculation show that the electron density distribution of HOMO and LUMO are both on the anthracene group, so there is not much difference of HOMO and LUMO energy level between these four materials. these compounds also exhibit good thermal stability with decomposition temperature in the range of 418~457 °C. The red and green phosphorescence device using these materials show the pretty good results, with lower turn-on voltage and higher current density compared to commercial Alq3. And using the best performed ETL, m-TPyAN to fabricated the double emission layer device, show the maximum E.Q.E of 11.5 %, higher than the single emission layer device with E.Q.E of 10.8 %.