Hole-Transporting Side-Chain Polymer Bearing a Thermally Crosslinkable Bicyclo[4.2.0]octa-1,3,5-trien-3-y1 Group for High Performing Thermally Activated Delayed Fluorescence OLED
- Authors
- Jeong, Cheol Hun; Godumala, Mallesham; Yoon, Jiwon; Choi, Suna; Kim, Yong Woo; Choi, Dae Hyuk; Cho, Min Ju; Choi, Dong Hoon
- Issue Date
- 15-5월-2019
- Publisher
- AMER CHEMICAL SOC
- Keywords
- hole-transport material; thermal crosslinking solution process; thermally activated delayed fluorescence; organic light-emitting diode
- Citation
- ACS APPLIED MATERIALS & INTERFACES, v.11, no.19, pp.17602 - 17609
- Indexed
- SCIE
SCOPUS
- Journal Title
- ACS APPLIED MATERIALS & INTERFACES
- Volume
- 11
- Number
- 19
- Start Page
- 17602
- End Page
- 17609
- URI
- https://scholar.korea.ac.kr/handle/2021.sw.korea/65408
- DOI
- 10.1021/acsami.9b03446
- ISSN
- 1944-8244
- Abstract
- A new side-chain polymer (X-TPACz) bearing hole-transporting pendant groups accompanying a thermally crosslinkable entity was synthesized using N-([1,1'-biphenyl]-4-y1)-N-(4-(9-(4-vinylbenzy1)-9H-carbazol-3-yl)pheny1)- bicyclo[4.2.0]octa-1(6),2,4-trien-3-amine (6) via addition polymerization. The X-TPACz could be spontaneously crosslinked without using any further reagents and showed a good film-forming property upon low-temperature thermal treatment. The thermal curing temperature for the X-TPACz film was optimized to be 180 degrees C based on a differential scanning calorimetry thermogram. Moreover, the thermal degradation temperature of X-TPACz measured to be over 467 degrees C using thermogravimetric analysis demonstrated that it shows excellent thermal stability. In particular, X-TPACz exhibits the highest occupied molecular orbital (HOMO) energy level to be -5.26 eV, which is beneficial for facile hole injection and transportation. Consequently, the thermally activated delayed fluorescence organic light-emitting diodes fabricated using X-TPACz as the hole-transporting material showed state-of-the-art performances with a low turn-on voltage (V-on) of only 2.7 V and a high external quantum efficiency (EQE) of 19.18% with a high current efficiency (CE) of 66.88 cd/A and a high power efficiency (PE) of 60.03 lm/W, which are highly superior to those of the familiar poly(9-vinylcarbazole) (PVK)-based devices (V-on= 3.9 V, EQE of 17.42%, with CE of 58.33 cd/A and PE of 33.32 lm/W). The extremely low turn-on voltage and high EQE were found to be due to the higher-lying highest occupied molecular orbital energy level (E-HOMO = 5.23 eV) and better hole transporting property of X-TPACz than those of PVK.
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