Abstract
We study the photoluminescence properties of the red-emitting phosphor Ca9Eu(VO4)7 and establish a strong red emission centered at 613 nm under excitation at 395 nm (near ultra violet light, near-UV light) due to the intra-configurational 5D0 → 7F2 transition within the 4f6 configuration of the Eu3+ ions. The intensity of the emitted light decreases with increasing temperature and at T = 470 K about 50% of the intensity of the emitted light at room temperature is lost. Five different red-LED prototypes were constructed by applying a mixture of Ca9Eu(VO4)7 phosphor and silicone gel on the headers of near-UV LED chips. The prototypes showed a color output from violet for the lowest phosphor concentration (133 g phosphor /l silicone gel), reaching an almost pure red-light output for the highest phosphor concentration (670 g phosphor /l silicone gel). The luminous efficiency of optical radiation (LER) was found to decrease slightly with increasing applied current. For the highest phosphor concentration, the LER decreases from 238 lmW−1 for 1 mA current supply to 235 lmW−1 for 18 mA current supply. The external quantum efficiency decreased from 7.33% for the lowest phosphor containing LED prototype to 4.13% for the highest one.
Highlights
The performance of Ca9Eu(VO4)[7] phosphor integrated on a LED base has not yet been evaluated, and key technological aspects, such as the luminous efficacy of optical radiation (LER) and color/intensity stability under typical pc-WLED operating conditions remain unclear
Here we investigate the PL properties, such as the excitation and emission spectra and thermal stability, of Ca9Eu(VO4)[7] phosphor under excitation in the near-UV range, as well as we evaluate the performance of a pc-LED prototype comprising a near-UV LED and Ca9Eu(VO4)[7] phosphor
Photoluminescence spectroscopy.—The PL excitation and emission spectra were measured at room temperature using a Fluorolog 3 spectrofluorometer from Horiba-Jobin-Yvon, equipped with a Xe lamp, a double excitation monochromator, a single emission monochromator and a photomultiplier tube (PMT) in photon counting mode for the detection of the emitted signal
Summary
UV to blue range, with no shift in the emission wavelengths,[18,22,23] suggesting it would be suitable for application in pc-WLEDs. the performance of Ca9Eu(VO4)[7] phosphor integrated on a LED base has not yet been evaluated, and key technological aspects, such as the luminous efficacy of optical radiation (LER) and color/intensity stability under typical pc-WLED operating conditions remain unclear. The PL emission spectrum (in red color in Fig. 2a) was measured for excitation at 395 nm in order to mimic the experimental conditions for the pc-LED prototype based on a near-UV LED and
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
