According to the latest contents of the international optical Journal opticsexpress, the research team of national Jiaotong University has developed a high-efficiency flexible white LED chip, which is expected to be applied in large area lighting, wearable equipment, display and other fields in the future.

Organic light emitting diodes (OLEDs) are commonly known when flexible sheet light sources are mentioned.
The flexible white LED, which is published in opticsexpress, is about 5x5cm in size. It uses a polyimide (PI) soft substrate, which is covered with a layer of copper foil. The electrode pattern is made by photolithography and oxygen plasma etching.
The research team used the crystallographic bonding technology to bond 81 1.143x1.143mm blue LED chips to the substrate with an anisotropic conductive film.
In order to produce white light, a layer of PDMS phosphor film should be added to the LED chip, including yellow phosphor "Y3Al5O12: Ce3 +" and red phosphor "caalsin3: Eu2 +". PDMS is nontoxic and nonflammable, with high transparency, high stability and high flexibility.
A flexible white LED sheet with a thickness of about 6 mm was successfully fabricated by using the coated led, PI substrate and PDMS phosphor film, which can emit warm white or cold white light. At the color temperature of 3000K and 5000K, the maximum luminous efficiency can reach 81lm / W and 120lm / W, respectively. Not only the luminous efficiency is high, but also the distribution of light source is uniform, the uniformity is 85%. As for the degree of flexibility, the radius of curvature can reach 15 mm.
The luminous flux does not have much influence on the deflection change, so it is suitable for the flexible display and lighting fixture
In addition, the flexible white LED is tested at 25 ℃ indoor temperature for 1000 hours of service life. The measured results show that the luminous efficiency loss is 2.5%, and it is estimated that the loss will be 22% in 10000 hours.
Although the service life is not as durable as ordinary LED lighting, under the continuous improvement of the overall performance of flexible white LED, it is expected to further break through the technology and introduce more applications in the future.