MANIPULATION OF ENERGY TRANSFER IN DELOCALIZED FRENKEL EXCITONS WITHIN MOLECULAR ASSEMBLIES

Our planet has an abundance of examples where nature excelled in design and creation of highly efficient photosynthetic energy transfer networks. In pursuit to harness these extraction and conversion mechanisms of solar power scientists have studied photosynthetic complexes from various organisms along with molecular aggregates and assemblies. As a result of these extensive investigations, organic semiconductors emerged as a promising tool for effective solar energy harvesting. However, despite their broad tunability and low cost, the implementation of organic molecules in photovoltaic devices is hindered by lower charge carrier mobility among other factors.

Excitation energy transfer between organic molecules in both photosynthetic pigment-protein complexes and semiconductors is accompanied by vibrational and electronic-vibrational interactions in the system. The multifaceted role of vibrations gives rise to a wide range of phenomena, yet at the same time, complicates the precise determination of their function in a given system. Understanding and isolating the vibrational contributions to energy transfer in molecular systems can unlock the full potential of organic semiconductors.

This work is another step toward the deliberate design of molecular-based systems. First, the fundamentals of molecular vibrations and their influence on energy transfer between molecules are discussed. Next, vibrational and electronic-vibrational effects are dissected in a naturally optimized pigment-protein complex. Finally, the role of vibrational interactions and dephasing effects are studied in a molecular aggregate-based exciton-polariton structure.