White light emission from blue InGaN LED with hybrid phosphor

In this work we fabricated white LEDs using a blue InGaN LED precoated conjugated copolymer/QDs composite (green-emitting Poly [(9,9-dioctyl-2,7-divinylenefluorenylene)-alto-co-(2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene)]/red-emitting CdSe quantum dots) as hybrid phosphor. The emission peak wavelengths of blue, green and red emissions in spectra are 462 and 618 nm respectively. Green-emitting polymer has two emission peaks (515 and 543nm). The subpeak of polymer (515 nm) is covered by absorption of QDs. Therefore the emission of first peak is decreasing as increasing the ratio of QDs while the emission of QD (618 nm) is increasing. Therefore CIE-1931 coordinate, the color temperature (Tc) and the color rendering index (Ra) were changed by the different ratio of QDs to copolymer. The white LED of the hybrid phosphor containing 20 wt% QDs has a luminous efficiency of 44.2 lm/W at 20 mA with a CIE-1931 coordinate of (0.3297, 0.3332), Tc of 5620 K and Ra of 75.3.