The present invention relates to an organic electroluminescent device comprising an anode, a cathode, an emission layer, an undoped electron transport layer comprising a first matrix compound, and an electron injection layer comprising a second matrix compound and an alkali organic complex and/or alkali halide, wherein the undoped electron transport layer and the electron injection layer are arranged between the emission layer and the cathode, wherein the reduction potential of the first matrix compound is less negative than, the reduction potential of 9,10-di(naphthalen-2-yl)anthracene and more negative than the reduction potential of 4,4′-bis(4,6-diphenyl-1,3,5-triazin-2-yl)biphenyl, wherein the reduction potential in both cases is measured against Fc/Fc.sup.+ in tetrahydrofurane; and the dipole moment of the first matrix compound is selected ≥0 Debye and ≤2.5 Debye and the dipole moment of the second matrix compound is selected >2.5 and <10 Debye.

An organic electroluminescence device includes: an anode; an emitting layer; and a cathode, the emitting layer containing a first material, a second material and a third material, the first material being a fluorescent material, the second material being a delayed fluorescent material, the third material having a singlet energy larger than a singlet energy of the second material.

A display substrate includes a base substrate and an encapsulation film disposed at a first side of the base substrate. At least one corner of an edge of the encapsulation film is a rounded corner or a substantially rounded corner.

A solar cell includes a first substrate, a first hole transport layer, a first photoelectric conversion layer containing a perovskite compound, and a second photoelectric conversion layer containing a photoelectric conversion material in this order. A band gap of the perovskite compound is greater than a band gap of the photoelectric conversion material. With respect to an absorption wavelength of the first photoelectric conversion layer 3, a refractive index n.sub.A of the first hole transport layer 2 satisfies refractive index of the first substrate≤n.sub.A≤refractive index of the first photoelectric conversion layer. Further, with respect to a transmission wavelength of the first photoelectric conversion layer 3 and an absorption wavelength of the second photoelectric conversion layer 5, a refractive index n.sub.B of the first hole transport layer 2 satisfies refractive index of the first substrate≤n.sub.B≤refractive index of the first photoelectric conversion layer.

An organic semiconductor device with low driving voltage is provided. The light-emitting device includes an anode, a cathode, and an EL layer between the anode and the cathode. The EL layer includes a hole-transport layer and alight-emitting layer. The hole-transport layer is positioned between the anode and the light-emitting layer. The hole-transport layer is not in contact with the anode. The hole-transport layer includes a transport layer material for a light-emitting device and the GSP_slope that is a potential gradient of a surface potential of an evaporated film of the material is higher than or equal to 20 (mV/nm).

A composition including a first compound and a second compound, wherein the first compound is an organometallic compound including platinum and a tetradentate ligand bound thereto, and the second compound is an organometallic compound including iridium, μ(Pt) is about 0.5 debye to about 5.0 debye, μ(Pt) is less than μ(Ir), μ(Pt) is a dipole moment of the first compound, μ(Ir) is a dipole moment of the second compound, and each of μ(Pt) and μ(Ir) is calculated based on density functional theory as described herein.

A novel light-emitting device that is highly convenient, useful, or reliable is provided. The light-emitting device includes a first electrode, a second electrode, and a first unit. The first unit is located between the first electrode and the second electrode, and the first unit has a function of emitting light. The first unit contains a light-emitting organic compound and an organic compound HRM. The organic compound HRM has four or more rotatable bonds and a principal moment of inertia. The principal moment of inertia includes a first normalized principal moment of inertia NPR1 and a second normalized principal moment of inertia NPR2 in a predetermined region.

An organic light-emitting device including a first electrode, a second electrode facing the first electrode, and an organic layer disposed between the first electrode and the second electrode, wherein the organic layer includes an emission layer, wherein the emission layer includes an electron transport host, a hole transport host, and a dopant, wherein the dopant includes an organometallic compound, and wherein the organometallic compound does not comprise iridium, wherein the organic light-emitting device satisfies predetermined parameters described in the specification.

An organic light-emitting device includes a mixed layer, an emission layer, and a buffer layer and satisfies one of Equation 1 or Equation 2 and Equation 3:

T1(D)≥T1(Mix)+0.3 eV  Equation 1

T1(H)≥T1(Mix)+0.3 eV  Equation 2

T1(Mix)<T1(Buffer)+0.5 eV.  Equation 3

A display device includes a display part including a first non-folding area, a second non-folding area, and a folding area between the first non-folding area and the second non-folding area, the folding area being foldable with respect to a folding axis, a window disposed on the display part, and an adhesive layer disposed between the display part and the window, the adhesive layer including a first adhesive material and a second adhesive material having an elongation rate greater than an elongation rate of the first adhesive material. The first adhesive material has a planar area greater than a planar area of the second adhesive material in each of the first non-folding area and the second non-folding area, and the second adhesive material has a planar area greater than a planar area of the first adhesive material in the folding area.