Role of CsF on electron injection into a conjugated polymer

We studied electron injection from Al and Au cathodes into the conjugated p olymer poly[2-methoxy,5-(2-ethylhexoxy)-1,4-phenylene vinylene] (MEH-PPV). When a thin CsF layer is inserted between MEH-PPV and Al, a substantial enh ancement in electron injection is observed. Insertion of the same layer bet ween MEH-PPV and Au does not have a similar effect, indicating that the enh ancement mechanism is specific to CsF and Al. Thin Cs layers enhance electr on injection regardless of the cathode metal. A mechanism that explains the se observations is proposed. (C) 2000 American Institute of Physics. [S0003 -6951(00)04341-2].