Kinetic pathway for interfacial electron transfer from a semiconductor to a molecule

Area of Science:

• Physical Chemistry
• Materials Science
• Photovoltaics

Background:

• Optimizing light-induced electron transfer is crucial for molecular solar energy conversion.
• Current methods focus on controlling distance and free energy at molecular-semiconductor interfaces.

Purpose of the Study:

• To investigate an alternative kinetic pathway for electron transfer at molecular-semiconductor interfaces.
• To explore the role of molecular bridges in controlling interfacial electron transfer kinetics.

Main Methods:

• Rational design of molecules with varied geometric torsion (xylyl- or phenylthiophene bridges) while keeping distance and driving force constant.
• Comparative studies of electron transfer rates through different bridge types.

Main Results:

• A significant bridge dependence on electron transfer rates was observed, not explained by distance or driving force.
• Electronic coupling through phenyl bridges was ten times greater than through xylyl bridges.
• Evidence suggests an interfacial electron transfer pathway utilizing aromatic bridge orbitals.

Conclusions:

• A novel kinetic pathway for interfacial electron transfer exists, offering a new control parameter for solar energy conversion.
• Aromatic bridge orbitals play a critical role in facilitating electron transfer at molecular-semiconductor interfaces.