Research & Projects

This project focuses on a theoretical and computational investigation of ultrafast charge transfer dynamics in donor–acceptor molecular systems, with particular emphasis on porphyrin-based donors and NTCDA acceptors. Charge-transfer processes play a central role in organic photovoltaics, photoactive materials, and molecular electronics, where efficiency is governed by the interplay among electronic structure, nuclear motion, and excited-state dynamics.

I chose to pursue this project to gain a deeper, mechanistic understanding of how molecular structure, electronic coupling, and vibrational dynamics influence charge separation and transport at the quantum level. While many experimental studies report high efficiencies in such systems, the underlying dynamical pathways are often not fully resolved. This work aims to bridge that gap by combining electronic structure calculations with nonadiabatic quantum dynamics simulations.

The project was carried out as part of my postgraduate research in theoretical and computational chemistry, under the guidance of my academic supervisor. I also benefited from discussions with peers and researchers working in excited-state dynamics and quantum chemistry. Computational resources and software tools used in this work include established quantum chemistry packages and the MCTDH program for wavepacket and nonadiabatic dynamics simulations. I gratefully acknowledge all institutional support and collaborators who contributed directly or indirectly to this research.

Objectives

The primary objective of this project was to develop a molecular-level understanding of charge transfer dynamics following photoexcitation in donor–acceptor systems.

Initially, the situation was that existing studies largely focused either on static electronic structure or phenomenological rate models, with limited insight into time-resolved population transfer and vibronic effects. My goal was to move beyond static descriptions and explicitly simulate the excited-state dynamics to reveal how charge transfer evolves in real time.

Specifically, this project aimed to:

• Analyze excited-state population dynamics and charge transfer pathways following photoexcitation.
  
  

• Investigate the role of molecular bridges and electronic coupling on charge separation efficiency.
  
  

• Understand how nuclear motion and vibronic interactions influence ultrafast electron transfer.
  
  

• Compare dynamical behavior across different system configurations to identify key design principles.
  
  

Throughout the project, essential considerations included the accuracy–cost balance of electronic structure methods, the choice of relevant nuclear degrees of freedom, and the physical interpretation of time-dependent quantum dynamics results.

Results

The simulations provided a detailed, time-resolved picture of charge transfer dynamics in the studied donor–acceptor systems. The results reveal that charge separation occurs on ultrafast timescales and is strongly influenced by electronic coupling and vibrational motion. Comparisons between systems with and without molecular bridges showed clear differences in population transfer rates and coherence effects, highlighting the critical role of molecular connectivity.

An important outcome of this work was the identification of specific vibrational modes that actively facilitate charge transfer rather than act as passive spectators. Surprisingly, certain nuclear motions were found to enhance charge-transfer efficiency by maintaining resonance between electronic states.

Beyond the scientific results, this project significantly deepened my understanding of nonadiabatic dynamics methods, including wavepacket propagation and surface coupling analysis. The insights gained here are expected to be valuable for future studies on photoactive materials and may contribute to the rational design of more efficient molecular systems for energy conversion and optoelectronic applications.