Organic Lighting Technologies developed a more efficient OLED design. Here's how they describe it:
"When OLEDs are driven at high current densities to increase the light output, it is widely known that fraction of holes leak towards the electrode without participating in recombination. This reduces the optical efficiency. To prevent this, the current state of the art employs ‘hole-blocking’ layer to impose energy barrier to holes. This is a fixed barrier and at high current densities, there can still be holes crossing this barrier. The patent issued to Organic Lighting Technologies LLC discloses a unique electrical method of applying electrical bias to retard the holes leaking to the electrode (cathode). This is accomplished through an electrically conductive and transparent porous layer in place of
‘hole-blocking’ layer. The advantage of this method against the traditional ‘hole-blocking’ layer is the bias that can be varied to exercise control over the holes leaking to the electrode. In fact the leakage of the holes can be modulated on demand. In addition, the electrons can also be prevented from leaking towards anode (without participating in recombination). This is done through the incorporation of an electrically conductive and transparent porous layer on the anode side. Suitable bias is applied across these two porous layers and the electrons and holes can be continuously modulated on demand. The trick here is to deposit these critical layers in the thin film organic stack without appreciably reducing the optical transparency."
This can be used for both lighting and displays (but will be especially useful in lighting because of the high-current densities used).
OLT has been issued a patent on this technique, and they plan to either license or sell this technology. We don't know yet how much more efficient will those OLEDs be. We'll have to wait for some company to license it...
