Approach to tune short-circuit current and open-circuit voltage of dye-sensitized solar cells: π-linker modification and photoanode selection

The modification of pi-linkers represents a viable strategy to improve the performance of organic dye in dye-sensitized solar cells (DSSCs). On the basis of the pi-linker modification, four cyclic thiourea functionalized dyes (AZ260, AZ261, AZ262, and AZ263) were synthesized and their effects on the short-circuit current density (J(sc)) and open-circuit voltage (V-oc) were investigated. The results showed that AZ261 bearing an n-hexyl chain on the p-linker generated higher J(sc) (16.02 mA cm(-2)) and V-oc (739.4 mV) than AZ6 without a substituent on the bithiophene (J(sc) = 15.89 mA cm(-2), V-oc = 729.2 mV, PCE = 7.20%), and a higher PCE of 7.42% was obtained from AZ261. Furthermore, insertion of a double-bond into the pi-linker (AZ263) yielded the highest J(sc) (17.83 mA cm(-2)) with a somewhat lower V-oc (719.2 mV), and delivered the highest PCE up to 8.24%. In addition, the function of mesoporous spherical TiO2 on the photoanodes were also systematically examined and proven to be beneficial in increasing the J(sc).