All-Solution-Processed Quantum Dot Light Emitting Diodes Based on Double Hole Transport Layers by Hot Spin-Coating with Highly Efficient and Low Turn-On Voltage

作者：Chen, Hongting; Ding, Ke; Fan, Lianwei; Liu, Wei; Zhang, Rui; Xiang, Songpo; Zhang, Qing; Wang, Lei^*

来源：ACS Applied Materials & Interfaces, 2018, 10(34): 29076-29082.

DOI：10.1021/acsami.8b06917

• quantum dot light emitting diodes
• hot spin-coating
• stepwise co-HTLs
• all-solution-processed
• charge injection balance

Poly(N,N'-bis-(4-butylphenyl)N,N'-bis (phenyl)benzidine) (poly-TPD) and poly(9-vinylcarbazole) (PVK) are both traditional hole transport layers (HTLs) in quantum dot light emitting diodes (QLEDs). Nevertheless, the low highest occupied molecular orbital of poly-TPD and poor hole mobility of PVK always result in poor performance of QLEDs when individually used as HTLs. Unfortunately, fabricating stepwise HTLs with poly-TPD and PVK faces technical problems until now. We demonstrate an effective method to construct the stepwise poly-TPD and PVK HTLs by utilizing the technique of hot spin-coating PVK in m-xylene on poly-TPD film. During this hot spin-coating process, the underlying poly-TPD remains unwashed and undamaged, benefiting the all-solution-processed QLED fabrication. The optimized all-solution-processed QLED with stepwise poly-TPD and PVK HTLs shows a maximum external quantum efficiency (EQE) of 15.3% and a maximum luminance of 17 110 cd/m(2) with a low turn-on voltage (v(on)) of 1.75 V. The maximum EQE is about 6.6 times higher than that of the reference QLED using a cold spin-coating process. The enhancement of the QLED performance can be attributed to the improvement of surface morphology and charge injection balance for the hot spin-coating stepwise co-HTLs based QLEDs. This work manifests the positive effect on performance boost by a hot spin-coating strategy toward stepwise co-HTLs formation and paves the way to fabricate highly efficient all-solution-processed light emitting diodes.

• 出版日期2018-8-29
• 单位华中科技大学