Effect of Thiophene Spacer Position in Carbazole‐Based Dye‐Sensitized Solar Cells on Photophysical, Electrochemical and Photovoltaic Properties

The synthesis, photophysical and electrochemical properties, and photovoltaic performances in dye‐sensitized solar cells (DSSCs) of five new metal‐free organic sensitizers with a carbazole moiety as the electron donor are reported. The compounds contain a thiophene at various positions and a cyanoacrylic acid unit as the electron acceptor. The position of the thiophene moiety affected both the photophysical and electrochemical properties, leading to conversion efficiencies of 1.44 to 4.57 % under AM 1.5 solar conditions (100 mW cm –2 ). The best performance and longest electron lifetime were found when a thiophene was located on both donor and acceptor sites. The DSSC showed a short‐circuit current ( J sc ) of 8.59 mA/cm 2 , an open‐circuit photovoltage ( V oc ) of 0.75 V, and a fill factor ( FF ) of 0.71. The position of the π‐conjugated bridges not only affects the absorption spectra and the energy levels of the sensitizers, but also adjusts the electron lifetime.