Efficient Red Phosphorescent Polymers with Trap-Assisted Charge Balance: Molecular Design, Synthesis, and Electroluminescent Properties
Autor: | Zhihua Ma, Wenyue Dong, Lixiang Wang, Jianhong Lü, Junqiao Ding |
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Rok vydání: | 2019 |
Předmět: |
chemistry.chemical_classification
Materials science Dopant chemistry.chemical_element Phosphor 02 engineering and technology Polymer Electroluminescence 010402 general chemistry 021001 nanoscience & nanotechnology Diphenylphosphine oxide 01 natural sciences 0104 chemical sciences chemistry Physical chemistry General Materials Science Iridium 0210 nano-technology Phosphorescence HOMO/LUMO |
Zdroj: | ACS Applied Materials & Interfaces. 11:18730-18738 |
ISSN: | 1944-8252 1944-8244 |
DOI: | 10.1021/acsami.9b03618 |
Popis: | Three classes of red phosphorescent polymers (PF-H- x, PF-DPO- x, and PF-DPA- x, where x denotes the mole content of Ir complex) have been designed and synthesized, where the C∧N ligand of the tethered dopant bis(2,4-diphenylquinolyl)iridium(acetylacetonate) is substituted by hydrogen (H), diphenylphosphine oxide (DPO), and diphenylamine (DPA), respectively. It is found that the electron-withdrawing DPO group can lower the lowest unoccupied molecular orbital (LUMO) level of the phosphor, whereas the electron-donating DPA group leads to an upshifted highest occupied molecular orbital (HOMO) level of the phosphor. Following a sequence of PF-DPA- x, PF-H- x, and PF-DPO- x, the electron trap depth between dopant and host is gradually up from 0.43 to 1.01 eV, and the hole trap depth is correspondingly down from 0.74 to 0.46 eV. As a result, PF-DPO- x achieves the most balanced charge transport in the emitting layer among these polymers, revealing a record-high luminous efficiency (LE) of 10.3 cd/A and Commission Internationale de L'Eclairage (CIE) coordinates of (0.62, 0.33) on the basis of the simple single-layer device structure. Compared with PF-H- x (3.8 cd/A) and PF-DPA- x (1.2 cd/A) containing the same Ir content, the significantly improved performance indicates that trap-assisted charge balance is a promising strategy to optimize the device efficiency of red phosphorescent polymers. |
Databáze: | OpenAIRE |
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