Ultrafast Photoinduced Dynamics of Quaterthiophene-Squaraine Hybrid Aggregates

Abstract

Photoinduced energy transfer, charge transfer, and generation of sufficiently long-lived charge-separated (CS) states in the aggregated oligothiophenes are always challenging. Herein, we have coupled quaterthiophene (QTH) with a squaraine (SQR) dye in hybrid aggregates. A detailed time-resolved investigation using transient absorption spectroscopy and global target analyses revealed ultrafast photoinduced energy and electron transfer from QTH aggregates to SQR aggregates and the formation of a long-lived CS state in these hybrids. The pulse width limited energy transfer (<120 fs) occurred from the S1(Agg.)Ex. state, and the electron transfer occurred from both the S1(Agg.)Ex. state and the S1(Agg.)Rlx. state of QTH aggregates to the SQR aggregates at the timescales 131.5 ps and 3.3 ns, respectively. The resulting CS state lived for more than 8 ns. Moreover, the electrons of the QTH aggregates were prohibited to relax via the dark state and were extracted to the SQR aggregates which would lead to their successful utilization toward light-harvesting applications.