Abstract: A polycyclic aromatic compound consisting of a substructure represented by Formula (1A) and at least two substructures represented by Formula (1B): (A to C ring is an aryl ring which may be substituted, RXD is an aryl which may be substituted and bonded to A ring via a dashed-line which is —X—, the substructure represented by Formula (1B) is bonded to a ring constituting atom of the aryl or heteroaryl ring in one selected from the group consisting of A ring, B ring and RXD, and C ring and RXE in another substructure represented by Formula (1B) at position *, C ring is bonded to the above-selected ring, RXE is an aryl which may be substituted and bonded to the above-selected ring or X, Y is B, X is >N—R (R is an aryl which may be substituted)) is useful as a material for an organic device.

Abstract: An organic electroluminescent device having a light-emitting layer, wherein the light-emitting layer contains a host compound having a boron atom and an oxygen atom in the molecule as a first component, a thermally assisting delayed fluorescent material such that the energy difference ?EST between the excited singlet energy level and the excited triplet energy level is 0.20 eV or less as a second component, and a fluorescent material as a third component, and has a high light emission efficiency.