Computationally Driven Design Principles for Singlet Fission in Organic Chromophores

Singlet fission is a new mechanistic pathway to overcome the Shockley-Queisser limit by generating twice the number of triplet excitons per singly absorbed photon in selected materials. The first step of the singlet fission (SF) is initiated by the capture of sunlight by chromophores in the visible region, which is the prime factor for subsequent transfer of the excited energies to the neighboring chromophores. The key electronic properties of organic chromophores for SF are dictated by the interplay of the electronic states involved in this process. The separation of two triplet excitons from the correlated-triplet pair strongly depends on the molecular structure and their packing motif though either a covalent or noncovalent packing orientation that controls the efficiency of SF. In this Feature Article, we discuss the SF mechanism considering the thermodynamic condition, its correlation to the molecular structure, and, finally, its effects on the triplet yield generation from the first-principles computation. The discussion ranges from the single molecule to a dimeric pair of crystalline states in the context of technological importance and design principle rules for SF. Finally, we end this Feature Article with a brief overview of the experimental findings of our proposed chromophores in terms of the applicability in SF.