Circularly Polarized Electroluminescence of Chiral Copper(I) Complexes of 1,1’-Binaphthalene-Functionalized 1,10-Phenanthroline
Zhi-Ping Kang, Lin‐Xi Shi, Y.-Q. Wei, Jinyun Wang, Xu-Yang Ding, Zhong‐Ning Chen
Abstract
This study is dedicated to the design and synthesis of novel yellow-emitting Cu(I) complex enantiomers, R / S -Phen-Cu-POP, where the Cu(I) center is chelated by chiral 1,1’-binaphthalene-functionalized 1,10-phenanthroline (Phen) and bis(2-diphenylphosphinophenyl)ether (POP). Photophysical characterization revealed that the quantum yield ( Φ em ) of R / S -Phen-Cu-POP in CH 2 Cl 2 solutions was only 1.4–1.6%, but it significantly increased to 73.0% ( R ) and 76.1% ( S ) in PMMA doping films. Circularly polarized luminescence (CPL) studies demonstrated solid-state photoluminescence asymmetry factors ( g PL ) of R / S -Phen-Cu-POP were +8.5 × 10 –3 and −8.6 × 10 –3 . Temperature-dependent emission spectra and lifetime studies identified a small singlet–triplet energy gap (Δ E ST = 0.073 eV), which facilitates reverse intersystem crossing (RISC) from the triplet (T 1 ) to the singlet (S 1 ) state, thus leading to the transformation of phosphorescence at low temperature to thermally activated delayed fluorescence (TADF) at ambient temperature. Solution-processed organic light-emitting diodes (OLEDs) achieved a maximum luminance of 1270 or 1379 cd/m 2, a current efficiency of 31.8 or 30.3 cd/A, a power efficiency of 14.8 or 14.4 lm/W, and an external quantum efficiency (EQE) of 11.9% or 11.3% for R -Phen-Cu-POP or S -Phen-Cu-POP, respectively. Furthermore, the devices displayed efficient circularly polarized electroluminescence (CPEL) with electroluminescence asymmetry factors ( g EL ) of +8.7 × 10 –3 and −8.0 × 10 –3 for R / S -Phen-Cu-POP .