Orbital alignment at poly[2-methoxy-5-( 2 ′ -ethylhexyloxy)- p -phenylene vinylene interfaces

The orbital alignment at poly[2-methoxy-5-( 2 ′ -ethylhexyloxy)- p -phenylene vinylene (MEH-PPV) interfaces to Au and highly oriented pyrolytic graphite (HOPG) was investigated using x-ray and ultraviolet photoemission spectroscopies in combination with in situ multistep electrospray based thin film deposition. The electrospray deposition method enables deposition of polymers in vacuum directly from solution. This allows the investigation of polymer interfaces without the use of spin coating. Hence interfaces without the presence of significant contamination can be prepared, similar to what is possible at small molecular interfaces using in-vacuum evaporation. The presented experiments suggest, in conjunction with earlier experiments on MEH-PPV/Ag and MEH-PPV/indium tin oxide interfaces, that the currently assumed vacuum level alignment at conjugated polymer interfaces may not hold in all cases.