Abstract
Here we report enhanced efficiency bulk heterojunction organic solar cells using blend films of regioregular poly(3-hexylthiophene) (P3HT) and 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)
C
61
(PCBM) that are subjected to a thermal annealing process. Blend films (
P
3
HT
:
PCBM
=
1
:
1
by weight) were prepared using chlorobenzene and 1,2-dichlorobenzene in order to investigate the role of the solvent. Irrespective of the chosen solvent, the optimal device annealing temperature was found to be 140°C. The highest power conversion efficiency, 3% under air mass 1.5 simulated solar illumination
(
100
mW
∕
cm
2
)
, was achieved by device annealing at 140°C for 15 min using blend films prepared from chlorobenzene (2.3% for 1,2-dichlorobenzene).