Abstract
Photoluminescence and transient absorption measurements of poly(9,9-dioctylfluorene-
alt
-benzothiadiazole) (F8BT) and
1
-
(
3
-
methoxycarbonyl
)
propyl
-
1
-
phenyl
-
(
6
,
6
)
C
61
(PCBM) blend films reveal that optical excitation of F8BT results in formation of the singlet and triplet excited states of PCBM. These observations are assigned to rapid
(
>
10
11
s
−
1
)
singlet energy transfer from F8BT to PCBM, followed by intersystem crossing to the PCBM triplet state.