A dibenzothiophene-based cross-linked hole transport material for high-performance blue quantum dot light emitting diodes

Quantum dot light emitting diodes (QLEDs) have become a promising technology for next generation displays due to their outstanding photometric performance. Cross-linked hole transport materials (HTMs) have attracted wide attention in the field of QLED because of their high thermal stability and excellent solvent resistance. However, the low carrier mobility of cross-linked HTM hinders the charge injection balance of blue QLEDs, preventing their efficiency from meeting the requirements for full-color display applications. Here, to improve the carrier transport performance of cross-linked HTMs, dibenzothiophene with a large conjugated structure was selected as the central structure to develop a cross-linked HTM (V-KSP). Compared with the reported V-CBP, V-KSP with the central conjugate structure shows lower effective mass of electrons and holes, which significantly improves the carrier mobility of V-KSP by two orders of magnitude, from 6.54 × 10−5 to 2.72 × 10−3 cm2 V−1 s−1. Benefiting from the remarkable improvement of charge transport properties, the external quantum efficiency (EQE) of blue QLED with V-KSP reaches 15.6%, with the deep blue emission of Commission International de I'Eclaialia (0.15, 0.03), which will be significantly higher than that of blue QLED with V-CBP (EQE = 11.5%). These results provide not only theoretical guidance for designing high-performance cross-linked HTMs but also more choices for fabricating high-performance blue QLED.