Rational design of D-π-A organic dyes to prevent “trade off” effect in dye-sensitized solar cells

Abstract It is an easy task to simulate the spectrum properties for the organic dyes applied in dye-sensitized solar cells (DSSCs) if the suitable method is chosen. However, it is still difficult to quantitatively determine the overall performance for them. In this work, the short-circuit photocurrent density ( J SC ) and open circuit photovoltage ( V OC ) are quantitatively calculated by combination of the density functional theory and first principle for DSSCs based on four different organic dyes, 2-((4′-((4-(bis(4-methoxyphenyl)amino)phenyl)diazenyl)biphenyl-4-yl)methylene)but-3-ynoic acid ( 1 ), 2-((5-(4-((4-(bis(4-methoxyphenyl)amino)phenyl)diazenyl)phenyl)thiophen-2-yl)methylene)but-3-ynoic acid ( 2 ), 3-(7-(4-((4-(bis(4-methoxyphenyl)amino)phenyl)diazenyl)-4 H -cyclopenta[2,1- b :3,4- b ′]-dithiophene)-2-cyanoacrylic acid ( 3 ), and 3-(7-(4-((4-(bis(4-methoxyphenyl)amino)phenyl)diazenyl)phenyl)-2,3-dihydrothieno[3,4- b ][1,4]dioxin-5-yl)-2-cyanoacrylic acid ( 4 ), in which the triarylamine is donor and the cyanoacrylic acid is acceptor along with variable π group. The 3 and 4 are new theoretically designed organic dyes on the basis of 1 and 2 with different electron-rich group as π group. Both J SC and V OC of 3 and 4 are improved as compared with those of 1 and 2 , which breaks the normal “trade-off” rule. As a result, the power conversion efficiency (PCE) of 3 and 4 is improved, especially for 3 . The aggregation effect is also considered to evaluate the overall performance, which is favorable to further enhance the reliability of theoretical design.