Cross-linkable hole transporting layers boost operational stability of high-performance quantum dot light-emitting device

We report on CdSe@ZnS light-emitting diodes (QLEDs) showing both high efficiency and long operational lifetime by introducing thermally cross-linkable 2,7-disubstituted fluorene-based triaryldiamine (VB-FNPD) as the hole transporting layer and 1,4,5,8,9,11-hexaazatriphenylene hexacarbonitrile (HAT-CN) as the hole injection layer. The green QLEDs achieved a maximum external quantum efficiency (EQE) of 8.0% and power efficiency (PE) of 32.1 lm W−1 with low efficiency roll-offs. More importantly, the corresponding QLED demonstrated a long lifespan in operation by simple encapsulation without desiccation. Under the initial luminance of 2000 cd m−2 and a continuous flow of constant current, the device still held luminance of 1000 cd m−2 after 50 h operation. The overall decay profile was fitted by two single exponential components, with time constants of 17.2 and ∼104 h, which is superior to that using the conventional polymer as the hole transporting layer. The thermally polymerizable hole transporting materials therefore offer an effective approach to realize both good efficiency and long-term stability in QLED.