A security element has at least two luminescent substances, in which the security element has a first and a second luminescent substance which have a substantially identical, joint emission band. The first or the second luminescent substance, or both luminescent substances, have at least one excitation band that leads to an emission at the joint emission band only in the case of the first or the second luminescent substance.

A security element has at least two luminescent substances, in which the security element has a first and a second luminescent substance which have a substantially identical, joint emission band. The first or the second luminescent substance, or both luminescent substances, have at least one excitation band that leads to an emission at the joint emission band only in the case of the first or the second luminescent substance.

According to one embodiment, there is provided a white light source system including white light sources. An absolute value of a difference between (P()V())/(P(max1)V(max1)) and (B()V())/(B(max2)V(max2)) for each of the white light sources satisfies a relational expression represented by

|((P()V())/(P(max1)V(max1))(B()V())/(B(max2)V(max2))|0.15

The white light source system has a light emission characteristic of white light emitted by the system is continuously changed along with an elapse of time by changing a mixing ratio of light beams from the white light sources.

According to one embodiment, there is provided a white light source system including white light sources. An absolute value of a difference between (P()V())/(P(max1)V(max1)) and (B()V())/(B(max2)V(max2)) for each of the white light sources satisfies a relational expression represented by

|((P()V())/(P(max1)V(max1))(B()V())/(B(max2)V(max2))|0.15

The white light source system has a light emission characteristic of white light emitted by the system is continuously changed along with an elapse of time by changing a mixing ratio of light beams from the white light sources.

A quantum dot-polymer composite including a polymer matrix; and core-shell quantum dots dispersed in the polymer matrix, wherein the core-shell quantum dots include a semiconductor nanocrystal core including indium, zinc, and phosphorus and a semiconductor nanocrystal shell disposed on the semiconductor nanocrystal core, the shell including zinc, selenium, and sulfur. The core-shell quantum dots do not include cadmium, the core-shell quantum dots are configured to emit green light, the core-shell quantum dots have a mole ratio of phosphorus to indium of greater than or equal to about 0.75, and the core-shell quantum dots have a mole ratio of zinc to indium of greater than or equal to about 35, and a method of producing the core-shell quantum dots, and a display device including a light emitting element that includes the quantum dot-polymer composite.

Quantum dot semiconductor nanoparticle compositions that incorporate ions such as zinc, aluminum, calcium, or magnesium into the quantum dot core have been found to be more stable to Ostwald ripening. A core-shell quantum dot may have a core of a semiconductor material that includes indium, magnesium, and phosphorus ions. Ions such as zinc, calcium, and/or aluminum may be included in addition to, or in place of, magnesium. The core may further include other ions, such as selenium, and/or sulfur. The core may be coated with one (or more) shells of semiconductor material. Example shell semiconductor materials include semiconductors containing zinc, sulfur, selenium, iron and/or oxygen ions.

The invention relates to a security element having at least two luminescent substances. The invention starts out from a security element having at least two luminescent substances, whereby the security element has a first and a second luminescent substance which have a substantially identical, joint emission band, whereby at least the first or the second luminescent substance, or both luminescent substances, have at least one excitation band that leads to an emission at the joint emission band only in the case of the first or the second luminescent substance.

The invention relates to a security element having at least two luminescent substances. The invention starts out from a security element having at least two luminescent substances, whereby the security element has a first and a second luminescent substance which have a substantially identical, joint emission band, whereby at least the first or the second luminescent substance, or both luminescent substances, have at least one excitation band that leads to an emission at the joint emission band only in the case of the first or the second luminescent substance.

A device for converting solar radiation is described wherein the device comprises an inorganic luminescent material comprising a host material doped with Mn.sup.5+ ions for converting radiation of the UV and/or visible part of the electromagnetic spectrum into radiation of the near-infrared radiation part of the electromagnetic spectrum, preferably the infrared part between 1150 nm and 1250 nm, preferably around 1190 nm (the infrared emission peak of Mn.sup.5+); or, an amorphous host material doped with Sm.sup.2+ or Tm.sup.2+ ions, the amorphous host material including the elements Al, Si, O and N (SiAlON) for converting radiation of the UV and/or visible part of the electromagnetic spectrum into radiation of a longer wavelength, preferably a longer wavelength between 650 nm and 800 nm or a longer wavelength of around 1140 nm; and, at least one photovoltaic device for converting at least part of the converted radiation into electrical power.

A device for converting solar radiation is described wherein the device comprises an inorganic luminescent material comprising a host material doped with Mn.sup.5+ ions for converting radiation of the UV and/or visible part of the electromagnetic spectrum into radiation of the near-infrared radiation part of the electromagnetic spectrum, preferably the infrared part between 1150 nm and 1250 nm, preferably around 1190 nm (the infrared emission peak of Mn.sup.5+); or, an amorphous host material doped with Sm.sup.2+ or Tm.sup.2+ ions, the amorphous host material including the elements Al, Si, O and N (SiAlON) for converting radiation of the UV and/or visible part of the electromagnetic spectrum into radiation of a longer wavelength, preferably a longer wavelength between 650 nm and 800 nm or a longer wavelength of around 1140 nm; and, at least one photovoltaic device for converting at least part of the converted radiation into electrical power.