Orange‐Red‐Light‐Emitting Field‐Effect Transistors Based on Phosphorescent Pt(II) Complexes with Area Emission

Two new heteroleptic Pt(II) complexes bearing an n‐hexyloxy substituted phenyllepidine‐based ligand and either a picolinate (pic) or acetylacetonate (acac) coligand are synthesized for use in organic light‐emitting field‐effect transistors (LEFETs). Both compounds are obtained in good yields via a short and straightforward synthetic route. It is found that while both Pt(II) complexes show good chemical stability and solubility, the coligand affects the photoluminescence quantum yield and crystal packing of the complexes. Although aggregate induced phosphorescence enhancement is not observed, it is found that high concentrations of the emitters in a poly[bis(4‐phenyl)(2,4,6‐trimethylphenyl)amine] host lead to improved charge injection in hybrid LEFETs. LEFETs with area emission, high ON/OFF ratios (>10⁶) and mobilities (≈1.3 cm² V⁻¹ s⁻¹), and external quantum efficiencies of up to 0.1% at the highest brightness of 855 cd m⁻² are demonstrated.