Spiro-based hole-transporting materials utilized in green perovskite quantum dot light-emitting diodes with high luminance

Abstract

Herein, two new spiro-cored hole-transporting materials (HTMs), termed HT1 and HT2, are designed and synthesized, breaking the symmetry of the classical HTM, spiro-OMeTAD, by introducing benzo[d]imidazole with diverse electron characteristics of two nitrogen atoms to improve their hole-transporting properties. Both HT1 and HT2 exhibited excellent thermal stability with glass transition temperatures (T_g) of 162 and 197 °C, respectively, and good hole transport capability with hole mobilities of 8.26 × 10⁻⁵ and 1.08 × 10⁻⁴ cm² V⁻¹ s⁻¹, respectively. When utilized in green perovskite quantum dot light-emitting diodes (Pe-QLEDs), the devices achieved low turn-on voltages of 3.0 and 2.8 V, maximum external quantum efficiency (EQE_max) of 7.6 and 6.7% and high maximum luminance of 45 056 and 46 382 cd m⁻², respectively. The excellent hole-transporting properties and great device performance show that HT1 and HT2 are promising HTMs for Pe-QLEDs.