Doping‐Free Organic Light‐Emitting Diodes with Very High Power Efficiency, Simple Device Structure, and Superior Spectral Performance

TLDR

Current phosphorescent OLEDs rely on host‑guest doping to reduce triplet quenching, but this process is complex and fabrication‑intensive. Device operation is governed by exciton and polaron dynamics within the layers. A neat Pt(II) complex emitter yields doping‑free white and yellow‑orange PhOLEDs with low voltages (2.2–2.4 V) and record power efficiencies (~80 lm W⁻¹ for yellow‑orange, 50 lm W⁻¹ for white) while maintaining color stability, thanks to the homogeneous emitting/transporting layer and ambipolar blue emitter.

Abstract

Today's state‐of‐the‐art phosphorescent organic light‐emitting diodes (PhOLEDs) must rely on the host‐guest doping technique to decrease triplet quenching and increase device efficiency. However, doping is a sophisticated device fabrication process. Here, a Pt(II)‐based complex with a near unity photoluminescence quantum yield and excellent electron transporting properties in the form of neat film is reported. Simplified doping‐free white PhOLED and yellow‐orange PhOLED based on this emitter achieve rather low operating voltages (2.2–2.4 V) and very high power efficiencies of approximately 80 lm W −1 (yellow‐orange) and 50 lm W −1 (white), respectively, without any light extraction enhancement. Furthermore, the efficient white device also exhibits high color stability. No color shift is observed during the entire operation of the device. Analysis of the device's operational mechanism has been postulated in terms of exciton and polaron formation and fate. It is found that using the efficient neat Pt(II)‐complex as a homogeneous emitting and electron transporting layer and an ambipolar blue emitter are determining factors for achieving such a high efficiency.