Direct optical probing of negative carriers from an operating [6,6]-phenyl C61 butyric acid methyl ester diode

We have performed spectroscopic measurements combining with the diode operation of [6,6]-phenyl C61 butyric acid methyl ester (PCBM) for directly characterizing the nature of its n -carriers. The measurements in the visible region reveal that electrons for the n -carrier generation are primarily accommodated into the t 1 g and t 1 u levels. The measurements in the near-infrared region indicate that the n -carriers of the PCBM diode are delocalized compared to the PCBM anions in solution. We also show that the frequency-dependence of the spectroscopic signals can estimate the lifetime of the n -carriers in the PCBM diode ( 23 μ s ) .