Light emission material and organic electroluminescence device including the same

An organic electroluminescence device, comprising:

• a first electrode;
• a hole transport region on the first electrode;
• an emission layer on the hole transport region;
• an electron transport region on the emission layer;
• and
• a second electrode on the electron transport region,
• wherein the emission layer comprises a first compound satisfying the following Equation 1:
• K2≥0.1K1, Equation 1
• wherein K1 is a sum of radiationless transition rate due to internal conversion from an n-th triplet excitation state to a lower order triplet excitation state including the lowest triplet excitation state,
• K2 is a reverse intersystem crossing transition rate from the n-th triplet excitation state to a singlet excitation state adjacent to the n-th triplet excitation state, and
• n is an integer of 2 or more, and
• the first compound is represented by Formula 1:
• wherein L1 is a divalent substituted or unsubstituted alkenyl group having 2 to 10 carbon atoms, or a substituted or unsubstituted arylene group having 6 to 30 carbon atoms for forming a ring,
• m is an integer of 0 to 3,
• wherein when m is 2 or more, a plurality of Li are the same or different,
• R1 to R6 are each independently selected from deuterium, a halogen atom, a cyano group, a substituted or unsubstituted silyl group, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted aryl group having 6 to 30 carbon atoms for forming a ring, and a substituted or unsubstituted heteroaryl group having 2 to 30 carbon atoms for forming a ring,
• Y1 and Y2 are each independently selected from hydrogen, deuterium, a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted aryl group having 6 to 30 carbon atoms for forming a ring, and a substituted or unsubstituted heteroaryl group having 2 to 30 carbon atoms for forming a ring, and
• a to f are each independently an integer of 0 to 4,
• provided that:
• R1 to R6 are each independently not a t-butyl group,
• when R1, R2, R5, and R6 are each a bromine atom, then m is an integer of 1 to 3,
• when a to f are each 0, then m is an integer of 1 to 3,
• when a to f are each 0, then (L1)m does not include a divalent biphenylene group and a divalent ethylene group,
• when a to f are each 0 and m is 2, then (L1)m does not include a divalent unsubstituted phenylene group and a divalent unsubstituted ethylene group,
• when m is 0,
• a case where a, b, e, and f are each 1 is excluded, and
• R1, R2, R5, and R6 are each independently a triphenylsilyl group, and
• when m is an integer of 1 to 3,
• at least one of R1, R2, R5, or R6 is a halogen atom, a cyano group, or a substituted or unsubstituted silyl group, or
• any of a, b, e, or d are each independently an integer of 2 to 4, or
• at least one of Y1 or Y2 is not hydrogen, and when one of Y1 or Y2 is hydrogen, the remaining one of Y1 or Y2 is not an unsubstituted phenyl group or an unsubstituted methyl group.