Calcium-doped TiO 2 microspheres and near-infrared carbazole-based sensitizer for efficient co-sensitized dye-sensitized solar cell

Here, we synthesized metal-free organic dye (CCPICPB) with two carbazole donor groups and two anchoring groups that exhibit a panchromatic absorption in the near-infrared range of up to 750 nm. To study the photophysical properties of synthesized CCPICPB dye, the UV–Vis and cyclic voltammetric experiments were studied and the obtained results were validated with theoretical simulation studies. After that, the solvothermal approach is used to synthesize pristine anatase and calcium (Ca)-doped TiO 2 microspheres with a smooth morphology. These microstructures are examined in depth using XRD, electron microscopy and electrochemical analysis methods. On TiO 2 and Ca-doped TiO 2 photoanode materials, we first evaluated the performance of CCPICPB dye. Upon our optimized experimental condition, the 3% Ca-TiO 2 photoanode-based device exhibits an efficiency of 4.04%, which is greater than that of the pristine TiO 2 photoanode-based device (2.93%). Because of the quicker electron transport in the Ca-TiO 2 film, the short-circuit current density and efficiency of DSSCs were improved. Moreover, when the CCPICPB dye was used as a co-sensitizer with the common Ru(II) dye (Z907), interestingly it showed the highest efficiency (6.11%) when compared with Z907 alone (5.12%). This improved efficiency of the co-sensitized device resulted from greater V OC conjugated with improved J SC . The J SC was improved because CCPICB dye could compensate for the photocurrent loss caused by redox electrolyte while the V OC was improved because electron recombination was inhibited under the co-sensitization conditions. Graphical abstract