Molecular engineering of thia-bridged triphenylamine heterohelicenes as novel organic dyes for dye-sensitized solar cells

Three organic sensitizers incorporating thia-bridged heterohelicene unit, thiophene-conjugate bridge, and cyanoacrylic acid were synthesized. The power conversion efficiency was quite sensitive to the substituents on heterohelicene donor group. Under standard global AM 1.5 solar conditions, the JK-206-sensitized cell gave a short-circuit photocurrent density (Jsc) of 13.44 mA cm−2, an open-circuit voltage (Voc) of 0.71 V, and a fill factor of 0.74, corresponding to an overall conversion efficiency of 7.08%. The device based on the JK-206 with an ionic liquid electrolyte showed an excellent long-term stability. The initial efficiency of 5.6% for JK-206 slightly decreased to only 5.4% after the 1000 h light soaking at 60 °C.