Issue 40, 2023

Long-term spontaneous negative aging behavior of encapsulated blue quantum dot light emitting devices: the influence of the hole transport material

Abstract

Encapsulated quantum dot light emitting devices (QLEDs) commonly exhibit a positive aging behavior, i.e., a spontaneous gradual improvement in their efficiency and performance during the first 10's of hours after encapsulation. In the long term, however, the trend reverses and the devices exhibit a spontaneous gradual deterioration in efficiency, a behavior referred to as negative aging. The root causes of this negative aging – which occurs without any electrical bias and therefore seriously limits the shelf life of QLEDs – remain unclear. Here, we carried out an in-depth analysis of the root causes behind the long-term spontaneous negative aging of encapsulated blue QLEDs. It is revealed that the long-term spontaneous negative aging is mainly due to the degradation of poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-(4,4′-(N-(4-butylphenyl))-diphenylamine)] (TFB), the most commonly used hole transport layer (HTL) material. Replacing TFB with 9,9-bis[4-[(4-ethenylphenyl)methoxy]phenyl]-N2,N7-di-1-naphthalenyl-N2,N7-diphenyl-9H-fluorene-2,7-diamine (VB-FNPD), a material that forms a cross-linked polymer, allows for preventing this negative aging behavior and maintaining the efficiency of the devices for over two months. This work provides design principles to realize long shelf-life QLEDs, and presents a new starting point for both fundamental studies and technological innovation.

Graphical abstract: Long-term spontaneous negative aging behavior of encapsulated blue quantum dot light emitting devices: the influence of the hole transport material

Supplementary files

Article information

Article type
Paper
Submitted
18 5 2023
Accepted
03 9 2023
First published
21 9 2023

J. Mater. Chem. C, 2023,11, 13788-13793

Long-term spontaneous negative aging behavior of encapsulated blue quantum dot light emitting devices: the influence of the hole transport material

J. Chen, A. Ghorbani, F. Samaeifar, P. Chun, Q. Lyu, G. Cotella, D. Song, Z. Xu and H. Aziz, J. Mater. Chem. C, 2023, 11, 13788 DOI: 10.1039/D3TC01720F

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