Organic electroluminescent materials and devices

A composition A comprising:

• a first dopant;
• and
• a first host;
• wherein:
• the first dopant has a HOMO energy HOMODopant and a LUMO energy LUMODopant,
• the first host has a HOMO energy HOMOHost and a LUMO energy LUMOHost;
• ❘
• "\[LeftBracketingBar]"
• LUMO
• Host
• -
• HOMO
• Dopant
• ❘
• "\[RightBracketingBar]"
• =
• X
• ⁢
• 1
• ;
• ❘
• "\[LeftBracketingBar]"
• LUMO
• Dopant
• -
• HOMO
• Host
• ❘
• "\[RightBracketingBar]"
• =
• X
• ⁢
• 2
• ;
• the first dopant has an optical bandgap energy, Y;
• at least one of X1 and X2 is less than or equal to Y+0.026 eV;
• the composition A has a vertical dipole ratio VDR(A);
• composition B is a reference composition comprising the first dopant and a second host, wherein the second host is
• the composition B having a vertical dipole ratio VDR(B);
• the ratio of the first dopant and the first host in the composition A is identical to the ratio of the first dopant and second host in the composition B;
• and
• VDR
• ⁡
• (
• A
• )
• -
• VDR
• ⁡
• (
• B
• )
• ⁢
• is
• ≥
• 0.05
• .