Organic electroluminescent element, organic electroluminescent unit, and electronic apparatus
An organic electroluminescent element includes, in order, a first electrode, an organic light-emitting layer, a buffer layer, a metal thin film, an organic electron transport layer, and a second electrode. The buffer layer includes an electrically-conductive organic material. The metal thin film includes a metal or a metal alloy. The organic electron transport layer is doped with a metal. The metal in the metal thin film is the same as the metal doped in the organic electron transport layer. The metal alloy in the metal thin film includes a metal that is the same as the metal doped in the organic electron transport layer.
1. An organic electroluminescent element comprising, in order:
a first electrode;
an organic light-emitting layer;
a buffer layer that includes an electrically-conductive organic material, wherein the buffer layer is in direct contact with the organic-light emitting layer;
a metal thin film that includes a metal or a metal alloy;
an organic electron transport layer doped with a metal;
a second electrode; and
the metal in the metal thin film being same as the metal doped in the organic electron transport layer, the metal alloy in the metal thin film including a metal that is same as the metal doped in the organic electron transport layer.
2. The organic electroluminescent element according to claim 1 , wherein the buffer layer satisfies following Expression (1):
|E 1− E 2|>0 Expression (1),
where E 1 denotes a work function of the metal thin film, and E 2 denotes a lowest unoccupied molecular orbital energy level of the buffer layer.
3. The organic electroluminescent element according to claim 2 , wherein the buffer layer satisfies following Expression (2):
0<| E 1− E 2|<0.6 eV Expression (2).
4. The organic electroluminescent element according to claim 1 , wherein the buffer layer includes an organic material that is free from forming a metal complex.
5. The organic electroluminescent element according to claim 1 , wherein the metal doped in the organic electron transport layer comprises a transition metal.
6. The organic electroluminescent element according to claim 5 , wherein the metal doped in the organic electron transport layer comprises ytterbium.
7. The organic electroluminescent element according to claim 1 , further comprising a film-thickness adjusting layer that is provided between the organic electron transport layer and the second electrode, and includes a transparent electrically-conductive material.
8. The organic electroluminescent element according to claim 1 , wherein a thickness of the metal thin film ranges from 0.1 nanometers (nm) to 2 nm.
9. The organic electroluminescent element according to claim 1 , wherein the metal thin film directly contacts the buffer layer, and the organic electron transport layer directly contacts the metal thin film.
10. The organic electroluminescent element according to claim 1 , further comprising a hole injection layer in contact with the second electrode.
11. The organic electroluminescent element according to claim 1 , further comprising a hole transport layer in contact with the organic light-emitting layer.