Printed OLED/ QLED Displays

OLED technology is increasing in the manufacture of flexible and foldable displays. It brings thinner, lighter, more energy-efficient and more powerful products. CleviosTM HIL materials improve the performance and processing of OLED displays.

Figure 1: Planarization and smoothing by Clevios™

Organic Light Emitting Diodes (OLEDs) have gained considerable momentum as a new display technology within the last decade. OLED displays are being increasingly adopted in smartphones and televisions and are considered the key technology for truly flexible displays in future.

OLED materials are mostly small organic molecules deposited by vacuum evaporation processes, which is one reason why OLEDs are more expensive than LCDs. An effective way to decrease costs in the future is the implementation of inkjet printing or coating processes to deposit the organic materials from the solution without the need for expensive vacuum equipment and processes.

Improved performance with Clevios™ as HIL

Heraeus provides a variety of aqueous and solvent-based dispersions of Poly(3,4-ethylenedioxythiophene) or PEDOT which help to improve performance and processing of OLED displays.

Clevios™ functions as hole-injection layer (HIL) between the anode and the OLED layer stack. It facilitates charge injection at low voltages and also improves efficiency by electron blocking, helping to improve an OLEDs’ lifetime.

Benefits of Clevios™ HIL materials:

  • Excellent transmission in the entire visible range from 380 – 800 nm
  • High transmission at even thick layers (> 100nm)
  • Excellent planarization properties of the anode and layers with low roughness (Figure 1)
  • Availability on a large-scale with installed production lines
  • Track record in PMOLED displays
  • Tunable work function (Φ = 4.8 eV to 5.9 eV), and resistivity (0,005 – 300 k
  • pH neutral aqueous types, e.g. Clevios™ P Jet (OLED)
  • pH neutral non-aqueous, organic solvent type, Clevios™ HIL 8 and Clevios™ HIL Jet 8
  • Inkjet printing, slot-die coating, and spin-coat versions