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

A family of new branched phosphine derivatives {Ph₂N–(C₆H₄)_<i>n</i>−}₃P → E (E = O <b>1</b>–<b>3</b>, <i>n</i> = 1–3; E = S <b>4</b>–<b>6</b>, <i>n</i> = 1–3; E = Se <b>7</b>–<b>9</b>, <i>n</i> = 1–3; E = AuC₆F₅ <b>4</b>–<b>6</b>, <i>n</i> = 1–3), which are the donor–acceptor type molecules, exhibit efficient deep blue room temperature fluorescence (λ_em = 403–483 nm in CH₂Cl₂ solution, λ_em = 400–469 nm in the solid state). Fine tuning the emission characteristics can be achieved varying the length of aromatic oligophenylene bridge −(C₆H₄)_<i>n</i>–. 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 formation and fluorescence self-quenching. Hence, compounds <b>2</b>, <b>3</b>, <b>5</b>, and <b>12</b> were used as emitters to fabricate nondoped and doped electroluminescent devices. The luminophore <b>2</b> (E = O, <i>n</i> = 2) demonstrates excellently balanced bipolar charge transport and good nondoped device performance with a maximum external quantum efficiency (EQE_max) of 3.3% at 250 cd/m² and Commission International de L’Eclairage (CIE) coordinates of (0.15, 0.08). The doped device of <b>3</b> (E = O, <i>n</i> = 3) shows higher efficiency (EQE_max of 6.5, 6.0 at 100 cd/m²) and high color purity with CIE (0.15, 0.06) that matches the HDTV standard blue. The time-resolved electroluminescence measurement indicates that high efficiency of the device can be attributed to the triplet–triplet annihilation to enhance generation of singlet excitons

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

A family of new branched phosphine derivatives {Ph₂N–(C₆H₄)_<i>n</i>−}₃P → E (E = O <b>1</b>–<b>3</b>, <i>n</i> = 1–3; E = S <b>4</b>–<b>6</b>, <i>n</i> = 1–3; E = Se <b>7</b>–<b>9</b>, <i>n</i> = 1–3; E = AuC₆F₅ <b>4</b>–<b>6</b>, <i>n</i> = 1–3), which are the donor–acceptor type molecules, exhibit efficient deep blue room temperature fluorescence (λ_em = 403–483 nm in CH₂Cl₂ solution, λ_em = 400–469 nm in the solid state). Fine tuning the emission characteristics can be achieved varying the length of aromatic oligophenylene bridge −(C₆H₄)_<i>n</i>–. 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 formation and fluorescence self-quenching. Hence, compounds <b>2</b>, <b>3</b>, <b>5</b>, and <b>12</b> were used as emitters to fabricate nondoped and doped electroluminescent devices. The luminophore <b>2</b> (E = O, <i>n</i> = 2) demonstrates excellently balanced bipolar charge transport and good nondoped device performance with a maximum external quantum efficiency (EQE_max) of 3.3% at 250 cd/m² and Commission International de L’Eclairage (CIE) coordinates of (0.15, 0.08). The doped device of <b>3</b> (E = O, <i>n</i> = 3) shows higher efficiency (EQE_max of 6.5, 6.0 at 100 cd/m²) and high color purity with CIE (0.15, 0.06) that matches the HDTV standard blue. The time-resolved electroluminescence measurement indicates that high efficiency of the device can be attributed to the triplet–triplet annihilation to enhance generation of singlet excitons