Luminescence of ZnS:Cu,Cl Phosphor Powder Excited by Photons, an Electric Field and Cathode Rays

Abstract

ZnS:Cu,Cl phosphor powder prepared by a solid state reaction at 900 o C showed a broad emission peak in 400-600nm, consisting of blue (440nm), self-activated (470nm) and green (510nm) bands. The emission color of the phosphor powder, originating from the relative intensity of these three bands, was found to depend on the excitation method, i.e., bluish green by photons, greenish blue under an electric field, and blue by cathode rays. This behavior was thought to result from the different penetration depth of excitation energy as well as from the spatial distribution of activators in the phosphor.

A Mechanoluminescent ZnS:Cu/Rhodamine/SiO2/PDMS and Piezoresistive CNT/PDMS Hybrid Sensor: Red-Light Emission and a Standardized Strain Quantification

“…The ML spectrum slightly differed from that of the PL spectrum for both ZnS:​Cu/​PDMS and ZnS:​Cu/​rhodamine/​SiO 2 /​PDMS composites, as shown in Figure a,b. It is very common that the PL spectrum differed from the electroluminescence (EL) and cathodoluminescence (CL) spectra for almost all ZnS-based luminescent materials with various dopants. − In addition, the emission peak wavelength varied with the applied voltage and frequency in the EL and CL situations and also varied with the excitation wavelength and excitation power in the PL situation. It is obvious that different centers and traps would operate in response to the excitation details (PL, EL, CL, ML, input power, frequency, wavelength, etc.…”

“…It is obvious that different centers and traps would operate in response to the excitation details (PL, EL, CL, ML, input power, frequency, wavelength, etc. ). − Such a complicated dopant (and defect) energy level distribution in the band gap constitutes a very complicated recombination process, ,, and the emission photon energy distribution depends on the relative contribution of each recombination process. A detailed discussion on this issue would be outside the scope of the present investigation.…”

“…Nondestructive ML has been recently realized via two brilliant types of materials, Sr­Al 2 O 4 (SAO) and ZnS series, with various doping elements. The SAO type includes Sr­Al 2 ­O 4 :​Eu; Sr­Al 2 ­O 4 :​Eu,Dy; and Sr­Al 2 ­O 4 :​Eu,Dy,Nd. − The ZnS type involves ZnS:​Mn; ZnS:​Cu,Al; ZnS:​Cu,Mn; and ZnS:​Cu,Cl. − The most promising level of ML was achieved by the green emissions from both SrAl 2 ­O 4 :​Eu and ZnS:​Mn. The SAO and ZnS-based ML materials exhibit an emission, color tuning possible from blue to red by varying the dopant. − For example, a red emission in ZnS:Mn was obtained through Te substitution at the Mn site. , There are also several other red-emitting mechanoluminescent materials, such as Pr 3+ activated calcium niobates composed of m CaO·​Nb 2 O 5 ( m = 1, 2, and 3) and MZn­OS:​Mn (M = Ba, Ca). − The CaZn­OS:​Mn 2+ /​epoxy resin ML composite with red emission was used for a mechanical stress sensor that can sense and image multiple mechanical stresses and decipher the stress intensity distribution .…”

Color Tuning in Electroluminescent Textiles

“…Various categories of luminescence are well described such as photoluminescence (PL), cathodoluminescence (CL), and electroluminescence (EL) depending on the external excitation sources. PL is excited by photons, EL by an electric field, and CL by electron rays [5]. This work is based on the physical phenomenon of electroluminescence: Luminophores (phosphors) are activated by an electrical field.…”