1 research outputs found
Investigation of Phase Separation in Bulk Heterojunction Solar Cells via Supramolecular Chemistry
In
this work, we have prepared two donor–acceptor–donor
(D-A-D) π-conjugated oligomers to investigate the effect of
phase separation on the performance of bulk heterojunction (BHJ) solar
cells. These charge transfer low band gap π-conjugated oligomers
(TTB and NMeTTB) were synthesized by Knoevenagel condensation of terthiophenecarbaldehyde
and barbiturate appended pyran derivative. The thin film morphology
of both the oligomers and along with electron acceptor [6,6]-phenyl-C60-butyric
acid methyl ester (PC<sub>61</sub>BM) was investigated by atomic force
microscopy (AFM) and transmission electron microscopy (TEM). The blend
of NMeTTB and PC<sub>61</sub>BM thin film yield highly ordered thin
film, whereas there was clear phase separation between TTB and PC<sub>61</sub>BM in thin film.The BHJ solar cell was fabricated using a
blend of NMeTTB and TTB with PC<sub>61</sub>BM acceptor in 1:1 ratio
as active layer, and a power conversion efficiency of 1.8% was obtained.
This device characteristic was compared with device having TTB:PC<sub>61</sub>BM as active layer, and large difference is observed in photocurrents.
This poor performance of TTB in BHJ devices was attributed to the
difference in the nanoscale morphology of the corresponding derivatives.
We rationalize our findings based on the low charge carrier mobility
in organic field-effect transistors and miscibility/phase separation
parameter of binary components (oligomers and PC<sub>61</sub>BM) in
the active layer of bulk heterojunction solar cells