Zn2Yb-Grafted and star-shaped metallopolymers for efficient near-infrared (NIR) polymer light-emitting diodes (PLEDs)

Abstract

Ring-opening metathesis polymerization (ROMP) of tetraallyl-functionalized complex monomer {[Zn₂(L)₄Ln(OAc)₂]·(NO₃)} (HL = 4-allyl-2-(1H-benzo[d]imidazol-2-yl)-6-methoxyphenol; Ln = Nd, 2; Ln = Yb, 3; or Ln = Er, 4) with NBE (norbornene) was used to prepare Zn₂Ln-containing star-shaped metallopolymers with desirable physical properties, including efficient Ln³⁺-centered NIR luminescence. Using metallopolymer poly(3-co-NBE), with its charge-facilitated and BCP-assisted carrier transport properties (BCP = 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline), as the emitting layer in a Yb³⁺-centered NIR-PLED afforded record electroluminescent properties (irradiance, 90.24 μW cm⁻²; efficiency, 0.065%) among previously reported organo-Yb³⁺-doped or organo-Yb³⁺-grafted polymer systems, with the advantages of a low turn-on voltage (5 V) and weak efficiency roll-off (≤30%) compared with organo-Yb³⁺-complex-based NIR-OLEDs.