LED dsiplay: light decay and material relationship

Light decay generally refers to its luminous flux. When charging the surface of the photosensitive drum, as the charge accumulates on the surface of the photosensitive drum, the potential also increases continuously, and finally reaches the “saturation” potential, which is the highest potential. The surface potential will decrease over time. Generally, the potential during operation is lower than this potential. The process of this potential naturally decreasing with time is called the “dark decay” process. When the photosensitive drum is scanned and exposed, the potential of the dark area (referring to the surface of the photoconductor that is not irradiated by light) is still in the dark decay process; The conductivity rises rapidly, forming the photoconductive voltage, the charge disappears rapidly, and the surface potential of the photoconductor also drops rapidly. It’s called “light decay”.

The light decay of LED products is the weakening of the signal of light during transmission. At this stage, LED products made by major LED manufacturers around the world have different degrees of light decay. High-power LEDs also have light decay, which is directly related to temperature. It is determined by the chip, phosphor and packaging technology.
At present, the luminous decay of white LEDs on the market may be one of the primary problems in entering civilian lighting. There are two main factors for the light decay of LED:

1. Quality problems of LED products themselves:
(1) The quality of the LED grains used is not good, and the brightness decays quickly.
(2) There is a defect in the production process, and the heat dissipation of the LED die cannot be well exported from the PIN pin, resulting in an excessively high temperature of the LED die and aggravated chip attenuation.
2, the use of conditions:
(1) The LED is driven by constant current, and some LEDs are driven by voltage to make the LED attenuate.
(2) The drive current is greater than the rated drive conditions.
In fact, there are many reasons for the light decay of LED products. The most important one is the heat problem. Although many manufacturers do not pay special attention to the heat dissipation problem in the secondary products, the light decay degree of these secondary LED products will be higher than that if they pay attention to heat dissipation for a long time. LED products are higher. The thermal resistance of the LED die itself, the influence of silver glue, the heat dissipation effect of the substrate, and the colloid and gold wires are also related to light decay.