Electron transport in a methanofullerene

The current-voltage characteristics of methanofullerene [6,6]-Ph C61-butyric acid Me ester (PCBM)-based devices are investigated as a function of temp. The occurrence of space-charge limited current enables a direct detn. of the electron mobility. At room temp., an electron mobility of me = 2 * 10-7 m2V-1s-1 has been obtained. This electron mobility is more than three orders of magnitude larger than the hole mobility of donor-type conjugated polymer poly(2-methoxy-5-(3',7'-dimethyloctyloxy)-p-phenylene vinylene) (OC1C10-PPV). As a result, the dark current in PCBM/OC1C10-PPV based devices is completely dominated by electrons. The obsd. field and temp.-dependence of the electron mobility of PCBM can be described with a Gaussian disorder model. This provides information about the energetic disorder and av. transport-site sepn. in PCB