OLED Lighting

Organic Light Emitting Diodes (OLEDs) have gained considerable momentum as a new technology for lighting within the last decade. Ultra thin and flexible form factors enable new luminare designs and unique lighting solutions.

Complexity and price

Although first products are in the market, OLEDs are still faced with major obstacles for OLED lighting to really expand into the general lighting market. Above all, high costs and competition with inorganic LEDs. This is in partly due to the intricate production process: OLED materials are evaporated by vacuum processes and expensive ITO sputtered anode substrates are used.

Cost control

Heraeus offers two OLED materials for solution processing (Figure 1, 2):

  • A hole-injection layer (HIL), between the anode and the OLED layer stack
  • A transparent, conductive electrode (anode) that can planarize a metal mesh or other rough electrodes, e.g. metal nanowires

  • Economic wet-processing by slot-die or inkjet coating
  • Excellent transmission even for thicker layers
  • Anode planarization function reduces OLED defects
  • Availability on a large-scale with installed production lines
  • Tunable work function and resistivity
  • pH neutral aqueous types as well as non-aqueous types
  • Controlled dispersion properties for very low layer roughness (Figure 3)

New Clevios™ HY E is a hybrid material of AgNW and PEDOT:PSS that enables sheet resistances as low as 10-15 Ohm/sq, for simple and busbar-free transparent anodes.

The advantages of planarization

A key feature of Clevios™ layers is their planarization property. Often underestimated in the lab, it’s advantages become obvious in production. Clevios™ can be coated as a thick yet highly transparent layer, allowing it to perfectly covers spikes, particles, and any rough surfaces which helps minimize leakage current, dark spots and defects in the OLED panels.

Combine for best results

A cost-attractive approach is the combination of Clevios™ with a printed silver metal-mesh. Clevios™ HIL-E can cover the rough metal mesh and renders a smooth transparent anode for the production of OLED lighting panels.

By planarizing the metal mesh, Clevios™ HIL-E with its high lateral conductivity ensures a uniform current distribution inside the mesh. For additional benefit it also works as efficient hole-injection layer. Clevios™ HIL-E beautifully combines three functions in a single material and layer:

  • Planarization
  • Electrode
  • HIL

In cooperation with KETI (Korea), Heraeus has successfully demonstrated this approach. (Figure 4)