  We report on terrylene-3,4:11,12-bis(dicarboximide) (TDI) as electron
acceptor for bulk-heterojunction solar cells using poly(3-hexyl thiophene)
(P3HT) as complementary donor component. Enhanced absorption was observed in
the blend compared to pure P3HT. As shown by the very efficient
photoluminescence (PL) quenching, the generated excitons are collected at the
interface between the donor and acceptor, where they separate into charges
which we detect by photoinduced absorption and electron-spin resonance (ESR).
Time-of-flight (TOF) photoconductivity measurements reveal a good electron
mobility of 10-3 cm2 V-1 s-1 in the blend. Nevertheless, the photocurrent in
solar cells was found to be surprisingly low. Supported by the external quantum
efficiency (EQE) spectrum as well as morphological studies by way of X-ray
diffraction and atomic force microscopy, we explain our observation by the
formation of a TDI hole blocking layer at the anode interface which prevents
the efficiently generated charges to be extracted.
