Mapping of band-bending for doped C60 films

We used a Kelvin probe to map band-bending occurring at interfaces between indium tin oxide electrodes and fullerene (C-60) films doped with either cesium carbonate (Cs2CO3) as a donor or molybdenum oxide (MoO3) as an acceptor. The carrier concentrations determined from the depletion layer widths coincided well with those obtained from the capacitance voltage characteristics. An ionization efficiency of 10% was determined for the molecularly dispersed dopant (Cs2CO3) in C-60, which is significantly lower than the corresponding value of 100% for phosphorus in silicon. (C) 2014 The Japan Society of Applied Physics