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 pi-pi 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 pi-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 pi-pi stacking and enhanced the hole-tran sporting properties of the polymers. Furthermore, the 3D pi-pi 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/m(2), respectively. The bulk heterojunction polymer phot3voltaic 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/cm(2), which were 3-5 times higher than that of the device based on P3 (0.09%) without triphenylamine side chains.