Tuning the photovoltaic parameters of spiro[fluorenexanthene]-diol (SFX-OH)-based crosslinked donor materials for efficient organic solar cells

Abstract

A group of donor-pi-acceptor (D-pi-A) type molecules designated as (X65-A, X65-B, X65-C, X65-D) have been designed by modifying spiro[fluorenexanthene] -diol (SFX-OH)-based, crosslinked reference molecule named as X65. The acceptor groups substituted are 2-Methylene-Malononitrile (X65-A), 2-Cyano-acrylic acid methyl ester (X65-B), 3-Methyl-5-Methylene-2-thioxo-thiazolidin-4-one (X65-C) and 2-(2-Methylene-3-oxo-indan-1-ylidene)-Malononitrile (X65-D). Frontier molecular orbitals (FMO) analysis, UV-vis spectral analysis, density of states (DOS), transition density matrix (TDM) analysis and reorganizational energies (RE) have been evaluated. Among newly reported compounds, X65-D has shown the lowest HOMO-LUMO band gap (1.18 eV) and highest value of lambda(max) (560 nm) and (533 nm) in gaseous and solvent (dichloromethane) medium, respectively due to its strong electron-pulling cyano (CN) moiety. The molecule X65-D has the lowest lambda(e) (0.00539 eV) and lambda(h) (0.00781 eV) values that demonstrates its enhanced charge mobility character. The highest dipole moment (14.77 D) has been reported for X65 B in dichloromethane demonstrating its improved solubility in solvent. To summarize in a nutshell all the afore-mentioned results, our current strategy has been proved auspicious in presenting a pathway for designing proficient photovoltaics. Our current study dictates that chnage in end-capped moiety is convincing tool to enhance the optoelectronic parameters of OSCs.All the newly engineered X65 based chromophores are proved as efficient donor materials and can be best candidates for practical applications.