Gate-tunable electroluminescence in Aviram-Ratner-type molecules: Kinetic description

Area of Science:

• Molecular electronics
• Organic electronics
• Quantum chemistry

Background:

• Electroluminescence (EL) in molecular junctions is crucial for organic electronic devices.
• Understanding the fundamental mechanisms of EL generation is key to device optimization.
• Aviram-Ratner-type molecules offer a platform for studying charge transport and light emission.

Purpose of the Study:

• To theoretically investigate the mechanisms of electroluminescence (EL) generation in photoactive molecules.
• To elucidate the role of molecular structure and electrode coupling in EL polarity.
• To analyze the control of EL power and critical voltages by gate voltage.

Main Methods:

• Theoretical study based on kinetics of single-electron transitions.
• Analysis of many-body molecular states.
• Derivation of analytical dependence of critical voltages.

Main Results:

• EL polarity originates from asymmetric coupling of molecular orbitals to electrodes.
• Gate voltage modulates EL power via control of excited singlet state occupancy.
• Orbital energy shifts create resonant or non-resonant electron transmission paths.
• Analytical expressions for critical voltages were derived, showing dependence on molecular state energies and gate voltage.

Conclusions:

• Asymmetric orbital coupling is the origin of EL polarity in these molecular systems.
• Gate voltage provides a mechanism for controlling EL intensity and activation thresholds.
• Understanding these mechanisms is vital for designing efficient molecular electronic devices.