Low-Temperature Cross-Linkable Hole Transport Materials for Solution-Processed Quantum Dot and Organic Light-Emitting Diodes with High Efficiency and Color Purity

• Published in: ACS applied materials & interfaces Vol. 15; no. 38; pp. 45167 - 45176
• Main Authors: Maheshwaran, Athithan, Bae, Hyejeong, Park, Jaehyoung, Jung, Hyeonwoo, Hwang, Youngjun, Kim, Jongyoun, Park, Chaehyun, Kang, Byeongjae, Song, Myungkwan, Lee, Youngu
• Format: Journal Article
• Language: English
• Published: American Chemical Society 27.09.2023
• Subjects: color; crosslinking; dibenzofuran; electrochemistry; energy; Organic Electronic Devices; phosphorescence; quantum dots; temperature; cross-linkable; hole transport material; quantum dot; solution-processed; light-emitting diode
• ISSN: 1944-8244; 1944-8252; 1944-8252
• DOI: 10.1021/acsami.3c09106

Cross-linkable hole transport materials (HTMs) are ideal for improving the performance of solution-processed quantum dot light-emitting diodes (QLEDs) and phosphorescent light-emitting diodes (OLEDs). However, previously developed cross-linkable HTMs possessed poor hole transport properties, high cross-linking temperatures, and long curing times. To achieve efficient cross-linkable HTMs with high mobility, low cross-linking temperature, and short curing time, we designed and synthesized a series of low-temperature cross-linkable HTMs comprising dibenzofuran (DBF) and 4-divinyltriphenylamine (TPA) segments for highly efficient solution-processed QLEDs and OLEDs. The introduction of divinyl-functionalized TPA in various positions of the DBF core remarkably affected their chemical, physical, and electrochemical properties. In particular, cross-linked 4-(dibenzo­[b,d]­furan-3-yl)-N,N-bis­(4-vinylphenyl)­aniline (3-CDTPA) exhibited a deep highest occupied molecular orbital energy level (5.50 eV), high hole mobility (2.44 × 10–4 cm2 V–1 s–1), low cross-linking temperature (150 °C), and short curing time (30 min). Furthermore, a green QLED with 3-CDTPA as the hole transport layer (HTL) exhibited a notable maximum external quantum efficiency (EQEmax) of 18.59% with a remarkable maximum current efficiency (CEmax) of 78.48 cd A–1. In addition, solution-processed green OLEDs with 3-CDTPA showed excellent device performance with an EQEmax of 15.61%, a CEmax of 52.51 cd A–1, and outstanding CIE­(x, y) color coordinates of (0.29, 0.61). This is one of the highest reported EQEs and CEs with high color purity for green solution-processed QLEDs and OLEDs using a divinyl-functionalized cross-linked HTM as the HTL. We believe that this study provides a new strategy for designing and synthesizing practical cross-linakable HTMs with enhanced performance for highly efficient solution-processed QLEDs and OLEDs.