Bis(diphenylamino)-benzo[4,5]thieno[3,2-b]benzofuran as hole transport material for highly efficient RGB organic light-emitting diodes with low efficiency roll-off and long lifetime

Abstract In this work, a novel hole transport material (HTM) based on benzo[4,5]thieno[3,2-b]benzofuran (BTBF) core with diphenylamine group, BTBF-DPA, was synthesized and systematically studied. BTBF-DPA showed high carrier mobility, good thermal stability and high triplet energy as 2.99 eV. Green phosphorescent organic light-emitting diodes (PhOLEDs) using BTBF-DPA were fabricated which displayed outstanding electroluminescent performance with a low turn-on voltage of 2.4 V, the maximum current efficiency (CE) of 123.6 cd A−1, power efficiency (PE) of 136.6 lm W−1, and external quantum efficiency (EQE) of 34.1%. Red PhOLEDs with BTBF-DPA also demonstrated a maximum PE of 40.1 lm W−1, and EQE of 24.9% with a low turn-on voltage of 2.3 V. Besides, blue fluorescence OLEDs presented a maximum PE of 4.9 lm W−1, EQE of 5.2% and small efficiency roll-off of 11.5% at 10000 cd m−2. RGB-OLEDs with BTBF-DPA outperformed the reference devices based on NPB as HTM that has been widely utilized. What's more, life-time of RGB OLEDs were T99 = 70 h at 10000 cd m−2, T70 = 60 h at 10000 cd m−2, T80 = 125 h at 5000 cd m−2, respectively. These results imply that BTBF-DPA is a promising HTM for OLEDs.