Efficient Red Phosphorescent Polymers with Trap-Assisted Charge Balance: Molecular Design, Synthesis, and Electroluminescent Properties

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.

Enhancing the electroluminescence performances of novel platinum(ii) polymetallayne-based phosphorescent polymers through employing functionalized IrIII phosphorescent units and facilitating triplet energy transfer

Novel phosphorescent polymers are developed with platinum(ii) polymetallayne-based backbones bearing functionalized Ir^III phosphorescent units to promote highly efficient triplet state energy-transfer and achieve high EL performances.

Platinum(ii) polymetallayne-based phosphorescent polymers with enhanced triplet energy-transfer: synthesis, photophysical, electrochemistry, and electrophosphorescent investigation

Promoting triplet energy-transfer in novel phosphorescent polymers with platinum(ii) polymetallayne backbones to achieve high EL performances with η_L of 11.49 cd A⁻¹, η_ext of 4.38% and η_P of 3.78 lm W⁻¹.