Efficient Violet Organic Light-Emitting Diodes with CIEy of 0.02 Based on Spiro Skeleton

摘要

Organic materials with violet electroluminescence are highly interesting for organic light-emitting diode (OLED) application. However, the design and synthesis of new molecules combining with desirable violet emission and high luminous efficiency are a challenging task. Here, three novel organic molecules consisting of a pyrene unit and a highly rigid skeleton, namely TFPy2, TFPy3, and TFPy4, are developed for violet-emitting OLEDs (VOLEDs). These emitters exhibit excellent thermal stability and violet emission with a narrow full width at half-maximum (FWHM) and high photoluminescence quantum yields (PLQYs). Photophysical results show that the emission peaks can be tuned by the introduction of pyrene units at different positions, and the emission will have a blue shift with increasing steric hindrance. Moreover, OLEDs fabricated with TFPy2, TFPy3, and TFPy4 as the emitters exhibit maximum external quantum efficiencies (EQEs), emission peaks, and CIEs (x,y) of 3.8, 414 nm, and (0.15, 0.03); 4.8, 406 nm, and (0.16, 0.02); and 5.1, 404 nm, and (0.16, 0.02), respectively. The two molecules TFPy3 and TFPy4 exhibit violet emissions with EL peaks at approximate to 405 nm with a record low CIEy of 0.02. Therefore, these materials and their construction strategy are promising for future VOLEDs with wide-color-gamut display and potential biological applications.