What are the performance indicators of LED
The latest advances in LEDs have led to a rapid growth in the lighting industry. At present, solid-state lighting technology gradually penetrate into different market segments, such as automotive lighting, indoor and outdoor lighting, medical applications, and daily necessities.
Quantum efficiency: The ratio of the number of electron-hole recombination (ie, the number of generated photons) to the total amount of radiation (radiation and non-radiation). This indicator determines the luminous efficiency of semiconductor materials. Semiconductor LED performance is usually expressed using external quantum efficiency (EQE), that is, IQE and extraction efficiency of the product. Extraction efficiency refers specifically to the part of the photon that fills the LED. EQE depends on the semiconductor layer defects that directly affect IQE and the device construction that affects the efficiency of extraction.
Luminous efficacy: luminous efficiency that the light source to launch visible light radiation efficiency, the unit is generally lm/W The light source is a single color green light (frequency 450x1012 Hz, the corresponding wavelength is about 555 nm, the human eye is the most sensitive light, Figure 2b for the corresponding eye sensitivity curve) to convert 100% of the energy, the maximum luminous efficiency of 683 lm/W. The white light source for lighting usually requires a wider emission spectrum than all the visible wavelengths, so its luminous efficiency is significantly lower than its maximum. Electric energy is converted to radiation beyond the eye sensitivity curve and cannot be used for lighting, and this type of radiation should be minimized.
Correlated color temperature: The reference light source used to compare different lighting techniques is a blackbody radiation in heat balance. According to Planck's law of radiation, the emission spectrum of a blackbody incandescent lamp depends on its temperature, and the color of the radiation corresponding to the different temperatures is represented by the CIE diagram, which is called the black spot of Planckian locus curve. Along the different positions of the Planck trajectory, the white CCT can be roughly divided into "warm white" (2,500-3,500 K), "natural white" (3,500-4,500 K), "cold White "(4,500-5,500 K) and daylight (5,500-7,500 K).
Color rendering index: CRI is a dimensionless indicator that describes the ability of a white light source to develop in an accurate and comfortable manner relative to human visual perception, taking into account the reference light source (the same CCT, the blackbody radiation in CCT < 6,000 K or natural light CCT> 6,000 K). CRI is usually defined as the average of 8 test color samples (R1-R8), with a rating range between 0 and 100. For high CRI with an additional R9 value, it means deep red. CRI = 100 means that all color samples illuminated by the test light source have the same color as the same sample that emits light from the reference light source.