Influence of π spacer of donor-acceptor-π-acceptor sensitizers on photovoltaic properties in dye-sensitized solar cells

Abstract

Abstract On the basis of organic dyes (E)-3-(6-(7-(bis(4-methoxyphenyl)amino)benzo[c] [1,2,5]thiadiazol-4-yl)-4,4-dimethyl-4H-cyclopenta[2,1-b:3,4-b']dithiophen-2-yl)-2-cyanoacrylic acid (1) and (E)-3-(6-(7-(bis(4-methoxyphenyl)amino)benzo[c] [1,2,5]thiadiazol-4-yl)-4-methyl-4H-dithieno[3,2-b:2′,3′-d]pyrrol-2-yl)-2-cyanoacrylic acid (2), two new D-A-π-A dyes, (E)-3-(7-(7-(bis(4-methoxyphenyl)amino)benzo[c] [1,2,5]thiadiazol-4-yl)benzo[2,1-b:3,4-b']dithiophen-2-yl)-2-cyanoacrylic acid (3) and (E)-3-(9-(7-(bis(4-methoxyphenyl)amino)benzo[c] [1,2,5]thiadiazol-4-yl)-2,3-dihydrodithieno[3′,2':3,4; 2″,3'':5,6]benzo[1,2-b] [1,4]dioxin-6-yl)-2-cyanoacrylic acid (4) are designed with diphenylamine as donor, 2-cyanoacrylic acid as acceptor along with different π group. Besides the frontier orbital energy levels and absorption spectra, the interfacial properties of dye-TiO2 adsorbed system is considered. After adsorption, the energy level of both dye and TiO2 surface shifts, which would affect the overall performance. More important, the short-circuit current density (JSC), open-circuit voltage (VOC), and photon-to-electron conversion efficiency (PCE) are calculated, which is helpful to determine the effect of π group on the donor-acceptor-π-acceptor dyes. The negative influence of aggregation for the dye-TiO2 adsorbed system is also considered to evaluate the overall photovoltaic performance. The molecular simulations are carried out to explore the dynamic properties of aggregation.