Display Device

A display device comprising:

• a first tandem light-emitting device;
• a second tandem light-emitting device;
• and
• a third tandem light-emitting device,
• wherein the first tandem light-emitting device, the second tandem light-emitting device, and the third tandem light-emitting device each comprise a first light-emitting layer, a second light-emitting layer, and an intermediate layer sandwiched between the first light-emitting layer and the second light-emitting layer,
• wherein the first light-emitting layer and the second light-emitting layer emit light with the same hue in each of the first tandem light-emitting device, the second tandem light-emitting device, and the third tandem light-emitting device,
• wherein the first light-emitting layer comprises a first emission center substance and a first host material,
• wherein the second light-emitting layer comprises a second emission center substance and a second host material,
• wherein the first light-emitting layer of the first tandem light-emitting device and the first light-emitting layer of the second tandem light-emitting device emit light with different hues,
• wherein the first light-emitting layer of the first tandem light-emitting device and the first light-emitting layer of the third tandem light-emitting device emit light with different hues,
• wherein the first light-emitting layer of the second tandem light-emitting device and the first light-emitting layer of the third tandem light-emitting device emit light with different hues, and
• wherein, in a film in which the first emission center substance is dispersed at greater than or equal to 0.5 wt % and less than or equal to 20 wt % in the first host material in each of at least two of the first tandem light-emitting device, the second tandem light-emitting device, and the third tandem light-emitting device, an orientation parameter a of a transition dipole moment of the first emission center substance is less than or equal to 0.25.

A display device comprising:

• a first tandem light-emitting device;
• a second tandem light-emitting device;
• and
• a third tandem light-emitting device,
• wherein the first tandem light-emitting device, the second tandem light-emitting device, and the third tandem light-emitting device each comprise a first light-emitting layer, a second light-emitting layer, and an intermediate layer sandwiched between the first light-emitting layer and the second light-emitting layer,
• wherein the first light-emitting layer and the second light-emitting layer comprise the same host material and the same emission center substance in each of the first tandem light-emitting device, the second tandem light-emitting device, and the third tandem light-emitting device,
• wherein the first light-emitting layer of the first tandem light-emitting device and the first light-emitting layer of the second tandem light-emitting device emit light with different hues,
• wherein the first light-emitting layer of the first tandem light-emitting device and the first light-emitting layer of the third tandem light-emitting device emit light with different hues,
• wherein the first light-emitting layer of the second tandem light-emitting device and the first light-emitting layer of the third tandem light-emitting device emit light with different hues, and
• wherein, in a film in which the emission center substance is dispersed at greater than or equal to 0.5 wt % and less than or equal to 20 wt % in the host material in each of at least two of the first tandem light-emitting device, the second tandem light-emitting device, and the third tandem light-emitting device, an orientation parameter a of a transition dipole moment of the emission center substance is less than or equal to 0.25.