Single-photon type organic electroluminescent element

A single-photon type organic electroluminescent element comprising:

• a first electrode having optical transparency;
• a second electrode;
• and
• a plurality of light-emitting layers disposed between the first and second electrodes, wherein
• the plurality of light-emitting layers stacked between the first and second electrodes each emit light having a different peak wavelength, and
• each of the light-emitting layers is disposed separately from the second electrode at such a position that optical resonance is generated by reflected light emitted from a predetermined light-emitting layer toward the second electrode and reflected by the second electrode to return, and light emitting from the predetermined light-emitting layer toward the first electrode,
• wherein a distance between a light-emitting center portion of a k-th light-emitting layer, “k” representing a natural number, counted from a side of the first electrode among the plurality of light-emitting layers and a portion of the second electrode which reflects light falls within a range of 0.9 to 1.1 times a resonance distance dk represented by the following Equation (1):
• d
• k
• =
• m
• k
• .
• ⁢
• λ
• k
• 4
• ⁢
• n
• [
• Numerical
• ⁢
• ⁢
• Formula
• ⁢
• ⁢
• 1
• ]
• wherein λk represents a peak wavelength of light emitted from the k-th light-emitting layer, n represents an average refractive index of a member placed between the k-th light-emitting layer and the second electrode, and mk is a positive odd number.