Theoretical designing of selenium heterocyclic non-fullerene acceptors with enhanced power conversion efficiency for organic solar cells: a DFT/TD-DFT-based prediction and understanding.

In this study, we have designed and explored a new series of non-fullerene acceptors for possible applications in organic solar cells. We have designed four molecules named as APH1 to APH4 after end-capped modification of recently synthesized Y6-Se-4Cl molecule. Density functional theory and time dependent-density functional theory have been employed for computing geometric and photovoltaic parameters of the designed molecules. Designed molecules have displayed high values of fill factor and FF%. Further, high mobility of electrons and holes between metal electrodes are also noted for designed molecules. Good values of open circuit voltage enhance the power conversion efficiency in the APH1-APH4. Frontier molecular orbitals analysis and excitation energy values suggested easy transportation of charges between molecular orbitals. Moreover, red-shifting in the absorption spectrum with high oscillating strength is also noted in APH1 to APH4 as compared to reference molecules. Results of different opto-electronic and photovoltaic parameters recommended that APH1 to APH4 are effective contributors for the development of high performance organic solar cells.