Investigation of electronic trap states in organic photovoltaic materials by current-based deep level transient spectroscopy

Current-based deep level transient spectroscopy was used to study trap states in poly(3-hexylthiophene-2,5-diyl) (P3HT), [6,6]-phenyl-C61 butyric acid methyl ester (PCBM), and P3HT:PCBM blend. The obtained spectra showed traps of 87 meV activation energy in pure P3HT and 21 meV for PCBM. The blend shows a complex emission rate spectrum consisting of several different emission rate bands in the range of 0.1–30 s−1, yielding activation energies between about 30 meV and 160 meV.