Star-shaped small donor molecules based on benzotriindole for efficient organic solar cells: a DFT study

Abstract

Context: The purpose of the S01-S05 series of end-capped modified donor chromophores is to amplify the energy conversion efficiency of organic solar cells. Using quantum chemical modeling, the photophysical and photoelectric characteristics of the S01-S05 geometries are examined.

Method: The influence of side chain replacement on multiple parameters, including the density of states (DOS), molecular orbital analysis (FMO_S), exciton-binding energy (E_b), molecular electrostatic potential analysis, dipole moment (μ), and photovoltaic characteristics including open circuit voltage (V_OC), and PCE at minimal energy state geometries, has been investigated employing density functional theory along with TD-DFT analysis. The molar absorption coefficient (λ_max) of all the proposed compounds (S01-S05) was efficiently enhanced by the terminal acceptor alteration technique, as demonstrated by their scaling up with the reference molecule (SR). Among all molecules, S04 has shown better absorption properties with a red shift in absorption having λ_max at 845 nm in CHCl₃ solvent and narrow energy gap (E_G) 1.83 eV with least excitation energy (E_x) of 1.4657 eV. All created donors exhibited improved FF and V_OC than the SR, which significantly raised PCE and revealed their great efficiency as OSC. Consequently, the results recommended these star-shaped molecules as easily attainable candidates for constructing extremely efficient OSCs.

Keywords: Benzotriindole; DFT; Intramolecular charge transfer; Non-fullerene acceptor; Open circuit voltage.