Linewidth-limited energy transfer in single conjugated polymer molecules.

Area of Science:

• * Physical Chemistry
• * Polymer Science
• * Spectroscopy

Background:

• * Understanding energy transfer in conjugated polymers is crucial for optoelectronic applications.
• * Previous studies often lacked single-molecule resolution, obscuring fundamental processes.
• * Rigid-rod conjugated polymers offer a model system for studying intramolecular energy dynamics.

Purpose of the Study:

• * To investigate intramolecular energy transfer at the single-molecule level in rigid-rod conjugated polymers.
• * To elucidate the role of spectral linewidth and temperature in controlling energy transfer dynamics.
• * To explore the emergence of collective fluorescence phenomena.

Main Methods:

• * Low-temperature single-molecule spectroscopy.
• * Gated fluorescence spectroscopy for real-time imaging.
• * Analysis of homogeneous and polarized emission from individual chromophores.

Main Results:

• * Identified homogeneously broadened, polarized emission from individual chromophore units on single polymer chains.
• * Observed real-time intramolecular energy transfer, with chains acting as weakly interacting chromophores.
• * Demonstrated that energy transfer is governed by chromophoric spectral linewidth, which is temperature-dependent.
• * Showed that linewidths exceeding intramolecular disorder induce incoherent coupling and collective fluorescence.

Conclusions:

• * Single-molecule spectroscopy provides unprecedented insight into energy transfer mechanisms in polymers.
• * Temperature-controlled spectral linewidths are a key factor in dictating energy transfer pathways.
• * Incoherent chromophore coupling and collective phenomena arise under specific spectral and temperature conditions.