How Organic Diodes Make Light Using Special Molecules

Eastman Kodak's 1982 patent on creating light-emitting diodes (OLEDs) using organic materials, specifically a layer of porphyrinic compounds to help inject electrical charges.

What it covers

This patent describes how to build a light-emitting device, like a tiny light bulb, using organic materials. It details an 'electroluminescent cell' with a light-producing layer sandwiched between two electrical contacts (an anode and a cathode). The key innovation is adding a special 'hole-injecting zone' made of a porphyrinic compound, like phthalocyanine, right next to the anode. This layer helps electrical 'holes' (think of them as positive charges) move more easily into the light-emitting layer, making the device work better.

What it doesn't cover

• —Electroluminescent cells that do not use organic materials for the light-emitting zone.
• —Devices where the hole-injecting zone is not made of a porphyrinic compound.
• —Cells that lack a distinct hole-injecting zone between the luminescent zone and the anode.
• —Electroluminescent cells where the binder material has a breakdown field strength below 10^5 volt/cm.

The clever bit

The crucial insight was realizing that a specific class of organic molecules, porphyrinic compounds, could act as an efficient 'bridge' to inject positive charge carriers (holes) into the organic light-emitting layer, significantly improving device performance and efficiency.

Why it matters

This patent is a foundational piece for modern organic light-emitting diode (OLED) technology. OLEDs are now ubiquitous in high-end smartphone screens, televisions, and flexible displays. The principles laid out by Ching W. Tang here enabled the development of efficient, thin, and flexible displays that revolutionized consumer electronics.

Real-world examples

• 1.Modern OLED displays in smartphones
• 2.OLED televisions
• 3.Flexible OLED screens