White luminescence from single-layer devices of nonresonant polymer blends

Poly( 9 , 9 ′ -dioctyl fluorene) (F8) and poly( 4 , 4 ′ -diphenylene diphenylvinylene) (PDPV) are conjugated polymers with optical transitions that are nonresonant thanks to the particular structural features of PDPV that yield a very large Stokes' shift ( ∼ 1.14 eV ) between absorption and emission spectra. We present steady-state and time-resolved photoluminescence (PL) experiments showing that F8:PDPV blends are "optically disconnected" systems for which the emission spectra and PL quantum yields are the linear combination of the contributions of the individual constituents with weights given by the respective absorption coefficients and concentration in the films. Single-layer light-emitting diodes incorporating F8:PDPV blends show white electroluminescence resulting from the simultaneous exploitation of the spectral features of both blend constituents (Commission Internationale de l'Eclairage, CIE, coordinates: x = 0.27 and y = 0.36 , in the case of 8:2 F8:PDPV molar ratio).