New Electron‐Transporting Materials Based on Pyrimidine and Thiazolopyridine Moieties for High‐Efficiency Organic Light‐Emitting Diodes

Abstract

Using the pyrimidine moiety with electron‐accepting capability and the thiazolopyridine moiety, commonly used as a moiety with an electron‐withdrawing group in organic semiconductors, for the first time 2‐(3‐(4,6‐di(phenanthren‐9‐yl)pyrimidin‐2‐yl)phenyl)thiazolo[5,4‐b]pyridine (DPPTP) is designed and synthesized to enhance electron transport capabilities compared to the conventional electron‐transporting layer, tris(8‐hydroxyquinoline)aluminum (Alq3). The photoluminescence maxima in solution and film states are observed at 391 and 410 nm, respectively. Although the photoluminescence quantum yield is relatively low at 2% in the solution state, it increases to 28% in the film state. The measured electron mobility values from the fabricated device range from 1.46 × 10−5 to 2.0 × 10−5 cm2 V−1 s−1, ≈5.7 times faster than the electron mobility of Alq3. In a fluorescent blue device utilizing the newly synthesized DPPTP as the electron‐transporting layer, the current efficiency is 4.36 cd A−1, and the external quantum efficiency is 3.76%, representing a 1.3‐fold improvement in efficiency compared to Alq3 devices.