The Study Of Effects Of Optical And Electrical Properties Of The Iridium Complexes Caused By Substituted Soluble Steric Hindrance Groups

Phosphorescent organic light-emitting diodes（Ph OLEDs） have gained considerable attention owing to their excellent light-emitting properties, overcoming the efficiency bottleneck limited by the singlet-to-triplet ratio. Among the phosphors, iridium（III）-based phosphorescent materials are attracting much attentions in the field of OLEDs because of their high phosphorescent quantum yield, color tenability and relatively short excited state lifetime. The discovery of solution-processable iridium（III）-based dendrimers with highly efficiency devices from simple architectures was an important step forward in the field of Ph OLED. One more step forward in the field was given the desire to print light-emitting devices, which would be much efficient in material consuming compared with spin-coating. The photoelectric properties of relative iridium complexes have been studied and their applications in Ph OLEDs were also explored. Details are as follows:（1）The design and synthesis of three iridium complex derivatives based on 1-Ntrimethylbenzene-2-phenyl-imidazole. To explore the relationship between molecule structure and physical properties, comparison of thermal stability, electrical properties and optical properties and OLED performance were conducted. Theoretical calculation indicated that the distribution of triplet level of the complexes were similar, suggesting the introduction of alkoxy benzene did not participate in the light-emitting behavior. Better separation of HOMO and LUMO reduced the electron repulsion, which leads to the increase of transition dipole moment and the reduction in emission efficiency. This study provided a valuable material designed tactics for highly emissive iridium complexes.（2）The design and synthesis of a series of FIrpic and Ir（dfppy）₃ based derivatives. The introduction of alkoxy group on trimethylbenzene made no change in emissive spectra but weakened the concentration quenching among the complexes and increased PLQY during the study of photophysical properties, while enhancing the thermal stability, and the regularity of film forming and emissive transient lifetime. In contrast, a larger conjugation alkoxy benzene also been introduced to FIrpic and Ir（dfppy）₃, the same enhanced effects were obtained, but the emissive spectrum was redshifted as the conjugation. Enhanced efficient Ph OLEDs were also obtained.（3）The design and synthesis of two types of materials which were suitable for non-host inkjet printing Ph OLED, iridium complex dendrimers and poly（dendrimers）. Comparison of photophysical properties, thermal stability, electrochemical properties and OLED performances, the results indicated that these almost had similar properities, but iridium complex dendrimers had higher PLQY and better OLED performances, while the poly（dendrimers） had higher viscosity for printing and better film-forming. Patterned Ph OLEDs made of these materials were successfully lightened.