Photoinduced charge carriers at surfaces and interfaces of poly[2-methoxy-5-(2 '-ethyl-hexyloxy)-1,4-phenylene vinylene] with Au and GaAs - art. no. 035325

The electronic structure and photoinduced surface/interface charge transfer processes have been studied in poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-ph enylene vinylene] (MEH-PPV) thin films spin-coated on Au and n-GaAs(111) su bstrates using surface photovoltage spectroscopy. The results show that the MEH-PPV film is a p-type semiconductor with an optical band gap of around 2.1 eV and a surface work function of 4.7 eV, and its photovoltaic response is dominated by its free surface rather than the interface with the substr ate. In addition, an acceptor surface state at 0.5 eV above the valence-ban d edge is found in films produced at law spinning rate, perhaps due to surf ace roughness. Efficient photoinduced electron injection from MEH-PPV films into the GaAs substrates is observed and found to have a strong dependence on the solvent used in the MEH-PPV spin deposition. These findings are dis cussed in view of the electronic and physical structure of the films.