Backlight module with composite color-conversion optical material

A backlight module, comprising:

• a light source emitting a blue light;
• a light guide plate optically coupled to the light source, and the blue light transmitting through the light guide plate;
• and
• a composite color-conversion layer disposed over the light guide plate, wherein the composite color-conversion layer comprises:
• a first layer, adjacent to the light source and comprising a plurality of first quantum dots, wherein the plurality of first quantum dots are a plurality of red quantum dots;
• a second layer, further away from the light source than the first layer and comprising a plurality of second quantum dots, wherein the plurality of second quantum dots are a plurality of cyan quantum dots;
• a third layer, disposed between the first layer and the second layer and comprising a plurality of third quantum dots, wherein the plurality of third quantum dots are a plurality of green quantum dots;
• and
• a fourth layer, disposed between the first layer and the third layer and comprising a plurality of fourth quantum dots, wherein the plurality of fourth quantum dots are a plurality of yellow quantum dots, wherein an emission wavelength of the plurality of first quantum dots is longer than an emission wavelength of the plurality of fourth quantum dots, the emission wavelength of the plurality of fourth quantum dots is longer than an emission wavelength of the plurality of third quantum dots, and the emission wavelength of the plurality of third quantum dots is longer than an emission wavelength of the plurality of second quantum dots.