A novel near-infrared-absorbing heptamethine-cyanine dye (KFH-3) that contains four n-butyl groups was synthesized for use in highly efficient dye-sensitized solar cells with porous zinc oxide (ZnO) prepared at low temperature, and resulted in remarkable performance characteristics, such as a conversion efficiency of 1.23% (AM 1.5) with an incident photon-to-current conversion efficiency (800 nm) of 33%, a short-circuit photocurrent density of 3.34 mA, an open-circuit photovoltage of 0.49, and a fill factor of 0.76, using almost solely the near-infrared region of sunlight.

New heptamethine–cyanine dyes were synthesized and used for dye-sensitization of porous zinc oxide cells in the near-infrared region (800 nm). The introduction of alkyl groups into the cyclohexene and indolenium moieties remarkably prevented H-aggregation of the dyes. Consequently, the photovoltaic performance of the dye-sensitized zinc oxide cells with DCA was improved; a solar-to-electricity conversion efficiency (η) of 0.67%, a short-circuit current density of 2.22 mA cm−2, an open-circuit photovoltage of 0.46 V, and a fill factor of 0.66 under standard AM 1.5 irradiation (100 mW cm−2).

Novel near-infrared (NIR)-sensitizing (up to 800 nm) simple asymmetric squaraine dyes (Sq 31 and Sq 33) carrying indoline moieties that did not require the introduction of any linker groups were developed. DSSCs fabricated with Sq 33 exhibited remarkable characteristics in the long-wavelength visible and NIR region (up to 800 nm), such as a conversion efficiency of 3.75% (AM 1.5G) with an incident photon-to-current conversion efficiency of 63% (650 nm), a short-circuit photocurrent density of 13.64 mA, an open-circuit photovoltage of 0.48, and a fill factor of 0.57.