Designing Singlet Fission Materials Using Excited State Aromaticity

ended

Singlet exciton fission is a carrier multiplication process in organic semiconductors that generates two electron-hole pairs for one photon absorbed, affording quantum efficiencies up to 200%. Photovoltaic devices based on singlet fission have received large attention recently for their potential in efficiency enhancement and to break the Shockley-Queisser limit on the efficiency of single-junction photovoltaics. Recent advancements in singlet fission have been materials-limited due to the rarity of molecules which meet the essential energetic requirement for the process, that the energy of the lowest triplet excited state be approximately half the energy of the lowest singlet excited state. Also important is to ensure the chemical stability of the candidate compounds that would broaden their application prospect. In this proposal, we exploit the excited-state aromaticity view to manipulate the excited state energy levels and build novel singlet fission candidates. Based on theoretical and experimental study, selective models will be evaluated, synthesized and analysed, aiming at a novel strategy for manipulating the excited state energy and stability of organic semiconductors with the aromaticity view. The main aimis to demonstrate highly stable, tuneable organic materials which undergo singlet fission through exploitation of the aromaticity of both the ground state and excited states and feasible design rules for these materials. The materials are expected to be promising candidates as singlet fission functional layer for solar cells and other multiple exciton generation applications. The result concept represents better understanding and tailoring excited state properties of organic semiconductors, which can be expended to wide range of materials with particular excited state nature for even wider application prospect.