Light-emitting device including fluorescent compound, electronic apparatus including light-emitting device, and fluorescent compound

A light-emitting device comprising:

• a first electrode;
• a second electrode facing the first electrode;
• and
• an organic layer disposed between the first electrode and the second electrode, the organic layer comprising an emission layer and a fluorescent compound,
• wherein, upon excitation, excitons in a 3n-π* excited state of the fluorescent compound migrate to a 1π-π* excited state of the fluorescent compound by reverse intersystem crossing with a Rate (rISC), and the excitons in the 1π-π* excited state undergo radiative transition to a ground state to emit light via fluorescence, and
• excitons in the 3n-π* excited state of the fluorescent compound migrate to a 3π-π* excited state of the fluorescent compound through reverse internal conversion with a Rate (IC),
• wherein a ratio of Rate (rISC) to Rate (IC) is 0.5 to 1.5,
• the index “3” in “3n-π*” and “3π-π*” represents a triplet state, and the index “1” in “1π-π*” represents a singlet state,
• Rate (rISC) is evaluated by Equation 1, and Rate (IC) is evaluated by Equation 2:
• Rate (rISC)=SOC2/(E(3n-π*)−E(1π-π*))2 Equation 1
• Rate (IC)=SOC2/(E(3n-π*)−E(3π-π*))2 Equation 2
• wherein, in Equations 1 and 2,
• SOC represents a spin-orbit coupling value,
• E(3n-π*) represents an energy level of the 3n-π* excited state,
• E(1π-π*) represents an energy level of the 1π-π* excited state,
• E(3π-π*) represents an energy level of the 3π-π* excited state, and
• SOC, E(3n-π*), E(1π-π*), and E(3π-π*) are each evaluated according to density functional theory,
• wherein the fluorescent compound is represented by Formula 1-1:
• wherein, in Formula 1-1, ring A1 is a C5-C60 carbocyclic group or a C1-C60 heterocyclic group,
• Z1 in Formula 1-1 is a group represented by Formula 2-1 or a group represented by Formula 2-2, and n1 is an integer from 0 to 20,
• Z2 in Formula 1-1 is a group represented by Formula 2-2, and n2 is an integer from 1 to 40,
• Land L2 in Formulae 2-1 and 2-2 are each independently a single bond, a C5-C60 carbocyclic group unsubstituted or substituted with at least one R10a, or a C1-C60 heterocyclic group unsubstituted or substituted with at least one R10a,
• a1 and a2 in Formulae 2-1 and 2-2 are each independently an integer from 1 to 20, and
• ring A1 in Formula 1-1 is a group represented by one of Formulae A1-1 to A1-4 and A1-6:
• wherein R1 and each R10a in Formulae 2-1 and 2-2, are each independently hydrogen, deuterium, —F, —Cl, —Br, —I, —SF5, a hydroxyl group, a cyano group, a nitro group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a substituted or unsubstituted C1-C60 alkyl group, a substituted or unsubstituted C2-C60 alkenyl group, a substituted or unsubstituted C2-C60 alkynyl group, a substituted or unsubstituted C1-C60 alkoxy group, a substituted or unsubstituted C3-C10 cycloalkyl group, a substituted or unsubstituted C1-C10 heterocycloalkyl group, a substituted or unsubstituted C3-C10 cycloalkenyl group, a substituted or unsubstituted C1-C10 heterocycloalkenyl group, a substituted or unsubstituted C6-C60 aryl group, a substituted or unsubstituted C6-C60 aryloxy group, a substituted or unsubstituted C6-C60 arylthio group, a substituted or unsubstituted C1-C60 heteroaryl group, a substituted or unsubstituted monovalent non-aromatic condensed polycyclic group, a substituted or unsubstituted monovalent non-aromatic condensed heteropolycyclic group, —N(Q1)(Q2),
• —Si(Q3)(Q4)(Q5), —B(Q6)(Q7), or —P(═O)(Q8)(Q9),
• b1 in Formulae 2-1 and 2-2 is an integer from 1 to 20,
• * in Formulae 2-1 and 2-2 indicates a binding site to an adjacent atom.

A light-emitting device comprising:

• a first electrode;
• a second electrode facing the first electrode;
• and
• an organic layer disposed between the first electrode and the second electrode, the organic layer comprising an emission layer and a fluorescent compound,
• wherein, upon excitation, excitons in a 3n-π* excited state of the fluorescent compound migrate to a 1π-π* excited state of the fluorescent compound by reverse intersystem crossing with a Rate (rISC), and the excitons in the 1π-π* excited state undergo radiative transition to a ground state to emit light via fluorescence, and
• excitons in the 3n-π* excited state of the fluorescent compound migrate to a 3π-π* excited state of the fluorescent compound through reverse internal conversion with a Rate (IC),
• wherein a ratio of Rate (rISC) to Rate (IC) is 0.5 to 1.5,
• the “3” in “3n-π*” and “3π-π*” represents a triplet state, and the “1” in “1π-π*” represents a singlet state,
• Rate (rISC) is evaluated by Equation 1, and Rate (IC) is evaluated by Equation 2:
• Rate (rISC)=SOC2/(E(3n-π*)−E(1π-π*))2 Equation 1
• Rate (IC)=SOC2/(E(3n-π*)−E(3π-π*))2 Equation 2
• wherein, in Equations 1 and 2,
• SOC represents a spin-orbit coupling value,
• E(3n-π*) represents an energy level of the 3n-π* excited state,
• E(1π-π*) represents an energy level of the 1π-π* excited state,
• E(3π-π*) represents an energy level of the 3π-π* excited state, and
• SOC, E(3n-π*), E(1π-π*), and E(3π-π*) are each evaluated according to density functional theory,
• wherein an absolute value of a difference between an energy level of the 3n-π* excited state in the fluorescent compound and the lowest energy level among energy levels of the 1π-π* excited state in the fluorescent compound is in a range of about 0 electron volts to about 0.15 electron volts.