Monochromatic LEDs

Oh JH, Kang H, Eo YJ, Park HK, Do YR (2015) Synthesis of narrow-band red-emitting K2SiF6 Mn phosphors for a deep red monochromatic LED and ultrahigh color quality warm-white LEDs. J Mater Chem C 3 607... 

Light emitted by an LED is nearly monochromatic (pseudomono-chromatic). LEDs are robust and their lifetimes are more than 100 000 hours. Spectral characteristics of exemplary LEDs in comparison with laser diodes (LD) are shown in Figure 4. 

The fourth technique for electron analysis measures a preselected set of zero or nearly-zero kinetic energy. While first known as TPE spectroscopy, when monochromatic synchrotron light was used, the addition of pulsed, tunable lasers has led to a totally new, extremely promising branch of PES, termed zero electron-kinetic-energy (ZEKE) PES or ZEKE spectroscopy18. We will describe it in detail later. 

Figure 141 shows the EL spectra from a microcavity (a) and conventional LED (b) based on the emission from an NSD dye forming a thin emitting layer of a three-organic layer device. It is apparent that the half-width of emission spectra from the diode with microcavity is much narrower than those from the diode without cavity. With 0 = 0°, for example, the half-width of the spectrum of the diode with cavity is 24 nm whereas that of the sample without cavity increases to 65 nm. According to Eq. (275), the resonance wavelength, A, decreases with an increase of 0 in agreement with the experimental data of Fig. 141. We note that no unique resonance condition in the planar microcavity is given due to broad-band emission spectrum of the NSD emission layer. Multiple matching of cavity modes with emission wavelengths occurs. Thus, a band emission is observed instead a sharp emission pattern from the microcavity structure as would appear when observed with a monochromator the total polychromic emission pattern is a superposition of a range of monochromatic emission patterns. The EL spectra...

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