Delayed fluorescence organic electroluminescent element

A delayed fluorescence organic electroluminescent element comprising a pair of electrodes composed of a positive electrode and a negative electrode and a light emitting layer disposed between the pair of electrodes, in which

• the light emitting layer comprises at least one of a polycyclic aromatic compound represented by the following general formula (1) and a polycyclic aromatic compound multimer having a plurality of structures represented by the following general formula (1)
• (In the above formula (1),
• ring A, ring B and ring C each independently represent an aryl ring or a heteroaryl ring, while at least one hydrogen atom in these rings may be substituted,
• Y1 represents B,
• X1 and X2 each independently represent N—R, R of the N—R is an optionally substituted aryl, an optionally substituted heteroaryl or alkyl, R of the N—R may be bonded to the ring A, ring B, and/or ring C with a linking group or a single bond,
• at least one hydrogen atom in a compound or a structure represented by formula (1) may be substituted by a halogen atom or a deuterium atom).