Ambipolar Phosphine Derivatives to Attain True Blue OLEDs with 6.5% EQE

A family of new branched phosphine derivatives {Ph2N-(C6H4)n-}3P → E (E = O 1-3, n = 1-3; E = S 4-6, n = 1-3; E = Se 7-9, n = 1-3; E = AuC6F5 4-6, n = 1-3), which are the donor-acceptor type molecules, exhibit efficient deep blue room temperature fluorescence (λem = 403-483 nm in CH2Cl2 solution, λem = 400-469 nm in the solid state). Fine tuning the emission characteristics can be achieved varying the length of aromatic oligophenylene bridge -(C6H4)n-. The pyramidal geometry of central R3P → E fragment on the one hand disrupts π-conjugation between the branches to preserve blue luminescence and high triplet energy, while on the other hand provides amorphous materials to prevent excimer form…