A light-emitting device having a fused cyclic compound includes: a first electrode; a second electrode facing the first electrode; an interlayer between the first electrode and the second electrode and including an emission layer; and a fused cyclic compound of Formula 1:

##STR00001## wherein, in Formula 1, the variables are as defined herein.

A compound comprising a first ligand L.sub.A having the formula ##STR00001##
Formula I, is disclosed. In Formula I, ring A is a five- or six-membered carbocyclic or heterocyclic ring; Y.sup.1 is selected from carbon and nitrogen; each of X.sup.1 to X.sup.4 is C or N; at least two adjacent R.sup.2s of ring B form a fused structure having the following formula: ##STR00002##
ring C is fused to ring B and the wavy lines are bonds attached to ring B; ring D and ring E are either a 5-membered aromatic ring or a 6-membered aromatic ring; each R.sup.1, R.sup.2, R.sup.3, R.sup.A, R.sup.B, R.sup.C, and R.sup.D is independently selected from a variety of substituents; ligand L.sub.A is coordinated to a metal M and, optionally, linked with other ligands; and M is optionally coordinated to other ligands. Organic light emitting devices and consumer products containing the compounds are also disclosed.

Disclosed are a QLED display panel and a preparation method thereof and a display apparatus. The QLED display panel includes: a base substrate; a second electrode, an electron transport layer, a quantum dot luminescent layer, a hole transport layer, a hole injection layer, and a first electrode disposed sequentially on the base substrate; and the QLED display panel further including: a first ionic coordination compound layer between the quantum dot luminescent layer and the hole transport layer.

The present invention relates to an organic electroluminescent device comprising a light-emitting layer comprising an electron-transporting host material and a hole-transporting host material, and to a formulation comprising a mixture of the host materials and to a mixture comprising the host materials. The electron-transporting host material corresponds to a compound of the formula (1) comprising diazadibenzofuran or diazadibenzothiophene units. The hole-transporting host material corresponds to a compound of the formula (2) from the class of the biscarbazoles or the derivatives thereof.

Disclosed are a series of photoisomeric compounds, preparation method therefor and device comprising the compounds, wherein a photoisomeric compound-graphene molecular junction device is formed by linking the photoisomeric compound to a gap of two-dimensional monolayer graphene having a nano-gap array via an amide covalent bond. When a single photoisomeric compound is bridged to the gap of the two-dimensional monolayer graphene having a nano-gap array, the devices have a reversible light-controlled switching function and a reversible electrically-controlled switching function. A molecular switch device prepared by the method can achieve a high reversibility and a good reproducibility. The number of light-controlled switching cycles can exceed 10.sup.4, and the number of electrically-controlled switching cycles can reach about 10.sup.5 or greater. Moreover, the above-mentioned reversible molecular switch device remains stable within a period of more than one year. In addition, flexible non-losable organic memory transistor devices and light-responsive organic transistor devices can be constructed using the above-mentioned series of photoisomeric compounds.

Disclosed are a QLED display panel and a preparation method thereof and a display apparatus. The QLED display panel includes: a base substrate; a second electrode, an electron transport layer, a quantum dot luminescent layer, a hole transport layer, a hole injection layer, and a first electrode disposed sequentially on the base substrate; and the QLED display panel further including: a first ionic coordination compound layer between the quantum dot luminescent layer and the hole transport layer.

The invention provides an all-day solar cell system that is capable of simultaneously generating and storing electricity, which allows efficient photocharge during the day and discharge at night.

An organic light-emitting device including a first electrode, a second electrode, and an organic layer between the first and the second electrode, wherein the organic layer includes an emission layer, and the emission layer includes a first compound as a hole transport compound, a second compound as an electron transport compound, and a third compound represented by Formula 1:

##STR00001##

wherein in Formula 1, M is a transition metal, and at least one selected from A.sub.1 and A.sub.2 includes at least one deuterium.

Provided are an organometallic compound of Formula 1, an organic light-emitting device including the organometallic compound, and a diagnostic composition including the organometallic compound.

##STR00001##

In Formula 1, ring A.sub.1, ring A.sub.3, and ring A.sub.4 are each independently a C.sub.5-C.sub.30 carbocyclic group or a C.sub.2-C.sub.60 heterocyclic group, and ring A.sub.2 is an N-containing 5-membered heterocyclic group.

A light-emitting element having low driving voltage and high emission efficiency is provided. In the light-emitting element, a combination of a guest material and a host material forms an exciplex. The guest material is capable of converting triplet excitation energy into light emission. Light emission from the light-emitting layer includes light emission from the guest material and light emission from the exciplex. The percentage of the light emission from the exciplex to the light emission from the light-emitting layer is greater than 0 percent and less than or equal to 60 percent. The energy after subtracting the energy of light emission from the exciplex from the energy of light emission from the guest material is greater than 0 eV and less than or equal to 0.23 eV.