Synthesis of new N, N-diphenylhydrazone dyes for solar cells: Effects of thiophene-derived π-conjugated bridge

Four novel D–π–A hydrazone dyes (HT, HM, HE, and HO) with an N, N-diphenylhydrazone moiety as the electron donor, different thiophene-derived π-conjugated bridges and a cyanoacrylic acid moiety as the electron acceptor have been designed and synthesized for the application in dye-sensitized solar cells. The influences of thiophene-derived bridges on the photoelectrochemical and photovoltaic performance of these hydrazone dyes were investigated. Results demonstrate that the introduction of 3,4-dialkyloxythiophene could red-shift the dye’s absorption spectrum due to the enhancement of the electron-donating ability of π-conjugated bridges. Importantly, electrochemical impedance spectroscopy analysis reveal that 3,4-dialkyloxythiophene bridge could change the charge recombination resistance at the TiO2/dye/electrolyte interface and as a result to improve the open-circuit photovoltage. Among the four dyes, HO exhibits the maximum power conversion efficiency of 5.83% (Voc = 0.65 V, Jsc = 12.69 mA/cm2, FF = 0.707) under simulated AM 1.5 irradiation (100 mW/cm2).

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► We synthesized four hydrazone dyes with different thiophene-derived bridges to apply in DSSCs.
► We fine tune the photoelectronic properties by alternating the thiophene-derived bridges.
► We obtained the best PCE of 5.83% from the HO dye with 3,4-dioctyloxythiophene bridge.