# 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. - **Patent:** US 4356429 - **Original title:** Organic electroluminescent cell - **Owner:** Eastman Kodak Co - **Granted:** 1982 - **Status:** Public domain (expired) - **Times cited:** 1,031 - **Field:** consumer_electronics, semiconductors, materials, telecommunications ## What it does 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 does NOT 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. ## Real-world examples 1. Modern OLED displays in smartphones 2. OLED televisions 3. Flexible OLED screens ## 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. ## Frequently asked questions ### What does How Organic Diodes Make Light Using Special Molecules cover? 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. ### Who owns patent US 4356429? Eastman Kodak Co owns this patent, granted in 1982. ### When does this patent expire? This patent has expired and is now in the public domain — anyone can use the invention freely. ### What is patent US 4356429 cited by? This patent has been cited by 1031 later patents that build on its ideas. ### What problem does this patent solve? 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. ### What does this patent NOT cover? Electroluminescent cells that do not use organic materials for the light-emitting zone. **Full plain-English explainer:** https://patentbrief.org/patent/us/4356429/oled-organic-light-emitting-diode **Original patent:** https://patents.google.com/patent/US4356429 --- _Source: PatentBrief — https://patentbrief.org. Patent facts are from public records; the plain-English explanation is PatentBrief's._ ## Related patents Semantically similar inventions in the PatentBrief corpus: - [How Liquid Crystal Displays (LCDs) Were Invented](https://patentbrief.org/patent/us/3322485/lcd-liquid-crystal-display) — This 1962 patent describes the first practical way to use organic liquid crystals to create a display that scatters light when an electric current is applied. - [How Nichia Created the First Practical Blue LED Electrodes](https://patentbrief.org/patent/us/5563422/blue-led-gallium-nitride) — A foundational patent describing the specific metal contacts needed to make gallium nitride LEDs efficient and commercially viable. - [Tiny Capsules for Electronic Paper Displays](https://patentbrief.org/patent/us/5961804/e-ink-electronic-paper-display) — MIT's 1999 patent on a special ink made of tiny capsules that can change color when an electric field is applied, forming the basis for early e-readers. - [How the First Infrared LED Was Invented](https://patentbrief.org/patent/us/3293513/infrared-led-biard-pittman) — Texas Instruments' 1962 patent for the first practical semiconductor diode that emits infrared light when electricity passes through it. - [How Lithium-Cobalt Battery Cathodes Were Invented](https://patentbrief.org/patent/us/4302518/lithium-ion-battery-cathode) — This 1981 patent details the chemistry behind the lithium-cobalt oxide cathodes that power almost every modern smartphone, laptop, and electric vehicle.