A quantum dot, and an ink composition, a light-emitting device, an optical member, and an apparatus, each including the quantum dot. The quantum dot includes: a nanoparticle; and at least one ligand on a surface of the nanoparticle, wherein the nanoparticle does not include mercury and cadmium, and the at least one ligand includes at least two thiol groups and at least one hydrophilic group.

Photovoltaic cells incorporating the compounds A/M/X compounds as hole transport materials are provide. The A/M/X compounds comprise one or more A moieties, one or more M atoms and one or more X atoms. The A moieties are selected from organic cations and elements from Group 1 of the periodic table, the M atoms are selected from elements from at least one of Groups 3, 4, 5, 13, 14 or 15 of the periodic table, and the X atoms are selected from elements from Group 17 of the periodic table.

The phosphor of the present invention comprises a crystal phase having a chemical composition represented by the following formula [2], the crystal phase having no garnet structure, and the phosphor having an emission peak in a wavelength range of 600 nm to 650 nm by being activated by at least Mn.sup.4+,
A.sup.2.sub.aiiB.sup.2.sub.biiC.sup.2.sub.ciiD.sup.2.sub.diiX.sup.2.sub.xii  formula [2].

Disclosed is a particle with a component (1) and a component (2), in which the component (2) covers at least a portion of the surface of the component (1), and the component (2) includes an organic silicon compound layer including a siloxane bond and an inorganic silicon compound layer including a siloxane bond.

The invention relates to a light-emitting component comprising a light-emitting section consisting of a Hex-Si.sub.1−xGe.sub.x compound material, said Hex-Si.sub.1−xGe.sub.x compound material having a direct band gap for emitting light.

The invention also pertains to a light-absorbing component comprising a light-absorbing section consisting of a Hex-S.sub.1−xGe.sub.x compound material, said Hex-Si.sub.1−xGe.sub.x compound material having a direct band gap for absorbing light.

A material represented by the following formula (I)
(M).sub.8M.sub.6M.sub.6O.sub.24(X,S).sub.2:Mformula (I).
Also disclosed is an ultraviolet radiation sensing material, an X-radiation sensing material, a device and a method for determining the intensity of ultraviolet radiation.

A material represented by the following formula (I)

(M).sub.8M.sub.6M.sub.6O.sub.24(X,S).sub.2:Mformula (I).

Also disclosed is an ultraviolet radiation sensing material, an X-radiation sensing material, a device and a method for determining the intensity of ultraviolet radiation.

The present disclosure provides a red phosphor powder, a preparation method thereof and a luminescent device comprising the red phosphor powder. The red phosphor powder comprises inorganic compounds containing an element A, an element D, an element X and manganese, wherein element A is one or more selected from a group of Li, Na and K and necessarily includes K; element D is composed of Ge and Si, or element D is composed of Si, Ge and Ti; and element X is one or more selected from a group of F, Br and Cl and necessarily includes F; and the inorganic compound has the same space group structure as K.sub.2GeF.sub.6, the space group structure being the hexagonal crystal system P-6.sub.3mc(186). The red phosphor powder has a uniform morphology, a high luminescent efficiency and a good stability.

The invention relates to a light-emitting component comprising a light-emitting section consisting of a Hex-Si.sub.1?xGe.sub.x compound material, said Hex-Si.sub.1?xGe.sub.x compound material having a direct band gap for emitting light. The invention also pertains to a light-absorbing component comprising a light-absorbing section consisting of a Hex-S.sub.1?xGe.sub.x compound material, said Hex-Si.sub.1?xGe.sub.x compound material having a direct band gap for absorbing light.

The present disclosure provides a red phosphor powder, a preparation method thereof and a luminescent device comprising the red phosphor powder. The red phosphor powder comprises inorganic compounds containing an element A, an element D, an element X and manganese, wherein element A is one or more selected from a group of Li, Na and K and necessarily includes K; element D is composed of Ge and Si, or element D is composed of Si, Ge and Ti; and element X is one or more selected from a group of F, Br and Cl and necessarily includes F; and the inorganic compound has the same space group structure as K.sub.2GeF.sub.6, the space group structure being the hexagonal crystal system P-6.sub.3mc(186). The red phosphor powder has a uniform morphology, a high luminescent efficiency and a good stability.