Role of indium chloride on the luminescence properties of PPV

We have investigated the influence of the addition of indium chloride (InCl3) on the luminescence properties of poly(p-phenylene vinylene) (PPV). We find that the photoluminescence (PL) efficiency of PPV converted on spectrosil, about 27%, is reduced to 21% upon addition of 0.5% molar of InCl3, but remains constant for further increase of the InCl3 concentration up to 10% molar. The PL efficiency of PPV converted on ITO also decreases from 19% to 11% by addition of InCl3, as observed for the PPV converted on spectrosil, with similar independence on the InCl3 concentration. Photothermal deflection spectroscopy (PDS) studies of the PPV–InCl3 blends show no evidence for subgap absorption bands, as expected for charge transfer doping. We consider that the decrease of the PL efficiency of PPV by addition of InCl3 is due to ion-induced exciton quenching.