Theory of plasmon enhanced interfacial electron transfer

Area of Science:

• Materials Science
• Physical Chemistry
• Nanotechnology

Background:

• Dye-sensitized solar cells (DSSCs) efficiency can be improved by incorporating metal nanoparticles (MNPs).
• MNPs enhance local fields through surface plasmon resonance, potentially increasing dye photoexcitation and charge separation.
• Previous theoretical work explored single MNP effects on perylene/TiO2 systems.

Purpose of the Study:

• To generalize previous theories to systems with multiple coupled MNPs (up to four).
• To investigate the impact of MNP coupling and altered molecular parameters on electron transfer dynamics.
• To quantify the enhancement factor for MNP-decorated DSSCs.

Main Methods:

• Utilized density matrix theory to describe charge injection dynamics, including optical excitation and electron transfer.
• Employed a tight-binding model for a large rutile TiO2 cluster (approx. 10^5 atoms) to simulate electron motion.
• Calculated the overall probability of electron injection into the TiO2 cluster after short optical excitation.

Main Results:

• Observed strong hybridization of plasmon excitations when MNPs are closely spaced, forming a broad resonance.
• Coupled MNPs lead to significant enhancement of light absorption and electron transfer.
• Calculated enhancement factors exceeding 500 for the MNP influence on electron injection.

Conclusions:

• Coupled metal nanoparticles offer a substantial pathway for enhancing DSSC performance.
• The theoretical framework accurately captures plasmon-enhanced electron transfer in complex MNP-dye-semiconductor systems.
• This approach provides a quantitative tool for designing more efficient MNP-based solar cells.