Abstract
This study demonstrates the flexible white LED structure with high lumen efficiency and uniform optical performance for neutral white and warm white CCT. Flip-chip LEDs were attached on a polyimide substrate with copper strips as electrical and thermal conduction paths. Yellow phosphors are mixed with polydimenthysiloxane (PDMS) to provide mechanical support and flexibility. The light efficiency of this device can reach 120 lm/W and 85% of light output uniformity of the emission area can be achieved. Moreover, the optical simulation is employed to evaluate various designs of this flexible film in order to obtain uniform output. Both the pitch between the individual devices and the thickness of the phosphor film are calculated for optimization purpose. This flexible white LED with high lumen efficiency and good reliability is suitable for the large area fixture in the general lighting applications. Another study demonstrates a novel package design to store colloidal quantum dots in liquid format and integrate it with standard LED. The high efficiency and high quality color performance for neutral white correlated color temperature can be demonstrated. The experimental results indicate that the LQD white light-emitting diode (LQD WLED) has high color quality and good reliability characteristic. The light efficiency and color rendering index (CRI) of the LQD WLED can reach to 268 lm/Wop and 95 respectively. Moreover, the glass box is employed to prevent from humidity and oxygen. With this encapsulation design, our quantum dot box can survive over 1000 hours of on-self storage time.