Effect of 3D π−π Stacking on Photovoltaic and Electroluminescent Properties in Triphenylamine-containing Poly(p-phenylenevinylene) Derivatives

Poly(p-phenylenevinylene) (PPV) derivatives containing the 3D π−π stacking structures of the triphenylamine moieties as two side chains have been synthesized by the Wittig−Horner reaction. The presence of 2,5-bis(4-(N,N-diphenylamino)phenylenevinylene units along these π-conjugated polymer backbone lowered the band gap, and thus the resulting polymers exhibited strong and broad absorption in the visible region. Triphenylamine groups effectively extended the conjugation length through 3D π−π stacking and enhanced the hole-transporting properties of the polymers. Furthermore, the 3D π−π stacking effects of the triphenylamine moieties on the properties of the polymer light-emitting devices (PLEDs) and photovoltaic solar cells were also investigated in detail. The maximum electroluminescence (EL) brightness of the single-layer light emitting devices for P1 and P2 achieved 3003 and 1697 cd/m2, respectively. The bulk heterojunction polymer photovoltaic cells (PPVCs) based on P1 or P2 and PCBM (1:1, w/w) showed power conversion efficiencies up to 0.27% and 0.45% under the illumination of AM 1.5, 90 mW/cm2, which were 3−5 times higher than that of the device based on P3 (0.09%) without triphenylamine side chains.