Rational Design of High-Efficiency Organic Dyes in Dye-Sensitized Solar Cells by Multiscale Simulations

The electrical and optical properties of four T-shaped (D)2–A−π–A organic dyes, 3-(5-(1,4-bis­(4-(diphenylamino)­phenyl)-6-methyl-6H-indolo­[3,2-b]­quinoxalin-8-yl)­furan-2-yl)-2-cyanoacrylic acid (1), 3-(5-(1,4-bis­(4-(diphenylamino)­phenyl)-6-methyl-6H-indolo­[3,2-b]­azaquinoxalin-8-yl)­furan-2-yl)-2-cyanoacrylic acid (2), 2-(5-(4,10-bis­(4-(diphenylamino)­phenyl)-5-methyl-5H-[1,2,5]­thiadiazolo­[3,4-b]­carbazol-7-yl)­furan-2-yl)-2-cyanoacrylic acid (3), and 3-(5-(4,10-bis­(4-(diphenylamino)­phenyl)-5-methyl-5H-[1,2,5]­oxadiazolo­[3,4-b]­carbazol-7-yl)­furan-2-yl)-2-cyanoacrylic acid (4) with triphenylamine as donor, furan as the π group, cyanoacrylic acid as acceptor, as well as different ancillary acceptors, are theoretically investigated by multiscale simulations. On the basis of the isolated dyes, the frontier molecular orbital, the Fürster resonance energy transfer, and absorption spectra are studied to explore the effect of different ancillary acceptors. After that, the dye–TiO2-adsorbed system is considered by first principle. On the basis of the adsorbed system, the accurate values of short-circuit current density, open-circuit voltage, and power conversion efficiency are calculated, which is helpful to distinguish various dyes. It is always a perplexing problem for previous theoretical studies. Additionally, the aggregation effect is also considered to evaluate the performance of the dyes. 6-Methyl-6H-indolo­[3,2-b]­azaquinoxaline and 5-methyl-5H-[1,2,5]­oxadiazolo­[3,4-b]­carbazole are testified to be suitable auxiliary acceptors. On comparing the D−π–A dye with the same donor, the π group, and acceptor, it is established that the insertion of the ancillary acceptor is important to improve the overall performance.