Improved efficiency and stability for acridine orange sensitizers by adding electron donating/accepting π-linker moieties

Abstract

Shortcomings associated with metal-free dye-sensitized solar cells can be overcome with dye modification. Using Density Functional Theory (DFT) and Time Dependent (TD-DFT), acridine orange dyes (main Donors) are modified with molecular moieties (2-Hydroxy-4-propoxyphen)(phenyl)methanone (UV absorber), 4,4′-Dimethoxydiphenylamine (Donor 1), 2-(Thiophen-2-yl)-1,3,4-oxadiazole (π-bridge), anisole (Donor 2), cyanoacetic-acid and carboxylic-acid functional groups (Acceptors 1 and 2), to form new UV Absorber-D-(A)2 and D’- π -D-(A)2 dyes with least computational costs, where acridine derivatives act as main donors. Absorption spectra, highest-occupied molecular orbitals, and lowest-unoccupied molecular orbitals are predicted by DFT and TD-DFT calculations. Ionization potential, electron affinity, electronegativity and light-harvesting efficiency are predicted with frontier-molecular orbital energies by Koopmans' theorem, using TiO2 conduction-band edge (ECB −4.0 eV) and [I-/I3-] redox-potential (-4.80 eV). Absorption redshifts with expanded range of 700 nm, and improved energy-alignment with TiO2, charge-transfer processes, redox-couple compatibility, cell stability and higher performance are all achieved by molecular level tuning of dyes.