Executive Summary : | The goal of this proposed project is to advance solar cell efficiency using computational tools to investigate singlet fission (SF) materials and design structurally enhanced novel chromophores. The SF process shows scope to improve the power conversion efficiency (PCE) in solar cells. In the SF process the high-energy singlet excited state (S₁) is split into two low-energy triplets (T₁) states producing an additional exciton for each absorbed photon. Owing to the process’s multiexciton production, SF has recently gained significant attention for its application in raising the Shockley-Queisser efficiency threshold in a single junction solar cell from 33.7% to 44.4%. The packing arrangements and structural parameters of the chromophores have a significant impact on the SF rate. The photobleaching of the S₀-S₁ transition was observed within the ultrafast time scale by pump-probe spectroscopy, due to the intermolecular coupling of excited states. As a result of such interactions, the recognition of excitons residing in excited states and their behaviour in numerous aggregated chromophores creates the need to develop novel techniques to understand its singlet fission mechanism. Early literature proposed SF as an intermolecular process that was sensitive to the orientation of crystal packing which made the structural design challenging. However, recently, intramolecular SF (iSF) has been reported in tunable bi-chromophoric structures with well-defined structure-property relationships. Here, the proposed project has three major goals: (i) to design materials exhibiting intermolecular SF by fine-tuning the morphological structure of chromophore pair or large aggregates for optimal coupling using computational tools (ii) to propose a new route to search for efficient SF materials (ii) To identify new molecules or reengineer/redesign existing Donor-Acceptor (D-A) molecules for iSF and suggest key parameters to screen conjugated D-A copolymer systems with the prospect of iSF function. Our objectives will be addressed through density functional theory (DFT), time-dependent DFT (TD-DFT), ab initio quantum dynamics, and wave-function calculations on the excited states and modelling the solid-state packing for singlet fission competent chromophores by incorporating dispersion interactions. This research has the potential to function as a theoretically reliable approach for predicting and developing novel SF (both intermolecular and intramolecular). Furthermore, this research attempts to boost photovoltaic performance beyond its current limits. |