Light emitting element and light emitting device

A light emitting element comprising:

• n pieces of layer groups (n is a natural number) between a pair of electrodes, each of the layer groups including:
• a first layer containing a substance that transports a hole easily and a substance with an electron accepting property;
• a second layer containing a substance that transports an electron easily and a substance with an electron donating property;
• and
• a light emitting layer provided between the first layer and the second layer,
• wherein in the n pieces of layer groups, the first layer included in the mth layer group (m is a natural number of 1≦m≦n) and the second layer included in the m+1th layer group are laminated in contact with each other.

A light emitting element comprising:

• n pieces of light emitting layers (n is a natural number) between a first electrode and a second electrode with higher reflectance than that of the first electrode;
• and
• a first layer containing a substance that transports a hole easily and a substance with an electron accepting property and a second layer containing a substance that transports an electron easily and a substance with an electron donating property between the mth light emitting layer (m is a natural number of 1≦m≦n) and the m+1th light emitting layer, the second layer being in contact with the first layer,
• wherein a peak wavelength of emission spectrum of the m+1th light emitting layer is shorter than that of the mth light emitting layer, and
• wherein the n pieces of light emitting layers are arranged such that the m+1th light emitting layer is placed closer to the second electrode than the mth light emitting layer.

A light emitting element comprising:

• n pieces of light emitting layers between a first electrode and a second electrode with higher reflectance than that of the first electrode;
• and
• a first layer containing a substance that transports a hole easily and a substance with an electron accepting property and a second layer containing a substance that transports an electron easily and a substance with an electron donating property between the mth light emitting layer (m is a natural number of 1≦m≦n) and the m+1th light emitting layer, the second layer being in contact with the first layer,
• wherein the n pieces of light emitting layers are arranged such that the light emitting layer exhibiting a shorter peak wavelength of emission spectrum is provided closer to the second electrode.

A light emitting element comprising:

• a first layer, a second layer formed in contact with the first layer, a third layer and a fourth layer formed in contact with the third layer between a first electrode and a second electrode, wherein the first layer and the third layer contain a substance that transports a hole easily and a substance with an electron accepting property, and the second layer and the fourth layer contain a substance that transports an electron easily and a substance with an electron donating property;
• a first light emitting layer emitting red light between the first layer and the first electrode;
• a second light emitting layer emitting green light between the second layer and the third layer, and
• a third light emitting layer emitting blue light between the fourth layer and the second electrode.

A light emitting element comprising:

• at least two light emitting layers between a first electrode and a second electrode;
• and
• a first layer containing a substance that transports a hole easily and a substance with an electron accepting property, and a second layer containing a substance that transports an electron easily and a substance with an electron donating property between a first light emitting layer and a second light emitting layer, the second layer being in contact with the first layer,
• wherein the substance with the electron accepting property is molybdenum oxide.

A light emitting element comprising:

• at least two layer groups between a pair of electrodes, each of the layer groups including:
• a first layer containing a substance that transports a hole easily and a substance with an electron accepting property;
• a second layer containing a substance that transports an electron easily and a substance with an electron donating property;
• and
• a light emitting layer provided between the first layer and the second layer,
• wherein in the layer group, the first layer included in a first layer group and the second layer included in a second layer group are laminated in contact with each other.

Alight emitting element comprising:

• at least two light emitting layers between a first electrode and a second electrode with higher reflectance than that of the first electrode;
• and
• a first layer containing a substance that transports a hole easily and a substance with an electron accepting property and a second layer containing a substance that transports an electron easily and a substance with an electron donating property between a first light emitting layer and a second light emitting layer, the second layer being in contact with the first layer,
• wherein a peak wavelength of emission spectrum of the second light emitting layer is shorter than that of the first light emitting layer, and
• wherein the light emitting layers are arranged such that the second light emitting layer is placed closer to the second electrode than the first light emitting layer.

A light emitting element comprising:

• at least two light emitting layers between a first electrode and a second electrode with higher reflectance than that of the first electrode;
• and
• a first layer containing a substance that transports a hole easily and a substance with an electron accepting property and a second layer containing a substance that transports an electron easily and a substance with an electron donating property between a first light emitting layer and a second light emitting layer, the second layer being in contact with the first layer,
• wherein the light emitting layers are arranged such that the light emitting layer exhibiting a shorter peak wavelength of emission spectrum is provided closer to the second electrode.