High-efficiency energy down-conversion system

An energy down conversion system that receives energy from outside and converts it into low energy,

• wherein the system comprises a multifunctional emitting compound;
• the multifunctional emitting compound includes a light emitting moiety and a light absorbing moiety;
• the light absorbing moiety absorbs energy and transfers it to the light emitting moiety;
• Formula 1 below is satisfied, in which a HOMO energy of the light absorbing moiety is E(1)HOMO, a LUMO energy of the light absorbing moiety is E(1)LUMO, a HOMO energy of the light emitting moiety is E(2)HOMO, and a LUMO energy of the light emitting moiety is E(2)LUMO;
• |E(1)HOMO−E(1)LUMO|≥|E(2)HOMO−E(2)LUMO| <Formula 1>
• Formula 2 below is satisfied when a wavelength of the light emitting moiety is greater than or equal to 350 nm and less than 2500 nm, in which an amount of light absorbed by the light emitting moiety is I(A), an amount of light emitted by the light emitting moiety is I(E), an amount of light absorbed by the light absorbing moiety is N(1), and an amount of light transferred to and emitted at the light emitting moiety is N(2);
• and
• 0.2×[I(E)÷I(A)]≤N(2)/N(1) <Formula 2>
• in the multifunctional emitting compound, the light emitting moiety and the light absorbing moiety are chemically connected so that a shortest distance between the moieties is within 10 Å.