Ultrafast Photoinduced Dynamics of Quaterthiophene-Squaraine Hybrid Aggregates

Photoinduced energy transfer, charge transfer, and generationofsufficiently long-lived charge-separated (CS) states in the aggregatedoligothiophenes are always challenging. Herein, we have coupled quaterthiophene(QTH) with a squaraine (SQR) dye in hybrid aggregates. A detailedtime-resolved investigation using transient absorption spectroscopyand global target analyses revealed ultrafast photoinduced energyand electron transfer from QTH aggregates to SQR aggregates and theformation of a long-lived CS state in these hybrids. The pulse widthlimited energy transfer (<120 fs) occurred from the S-1(Agg.) (Ex.) state, and the electron transfer occurred from boththe S-1(Agg.) (Ex.) state and the S-1(Agg.) (Rlx.) state of QTH aggregates to the SQR aggregates atthe timescales 131.5 ps and 3.3 ns, respectively. The resulting CSstate lived for more than 8 ns. Moreover, the electrons of the QTHaggregates were prohibited to relax via the dark state and were extractedto the SQR aggregates which would lead to their successful utilizationtoward light-harvesting applications.

Automated summary

This study investigates the photoinduced energy and electron transfer processes between quaterthiophene (QTH) and squaraine (SQR) dye in hybrid aggregates. The results show that energy transfer from QTH aggregates to SQR aggregates occurs within 120 fs, while electron transfer occurs at timescales of 131.5 ps and 3.3 ns, leading to the formation of a long-lived charge-separated state for more than 8 ns.