Fabrication and characterization of Cesium-doped Tungstate nanorods for Near-Infrared light absorption in dye sensitized solar cells

Near-infrared (NIR) light-absorbing materials have been widely used in vehicle and building applications due to their transparent film structure with a high absorption rate in the NIR range and a high transmittance rate for visible light. In this paper, Cesium-doped Tungstate (Cs0.33WO3) has been combined with dye-sensitized solar cell (DSSC) to convert the heat energy (absorbed from NIR light) into photocurrent. Cs0.33WO3 Nanorods were synthesized and embedded in the active layer of the cell. The mesoporous Titanium dioxide (TiO2) on FTO has also been used as the electron transport layer (ETL). This simple structure of FTO/TiO2/Cs0.33WO3 resulted in a poor Fermi level alignment and a low voltage. However, a buffer layer made of Poly[(9,9-bis(3′-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN-DOF) improved the Fermi level alignment and the quality of the interface in the modified structure of FTO/TiO2/PFN-DOF/Cs0.33WO3 which improved the initial Jsc from 0.38 μA/cm2 to 0.45 μA/cm2 for the NIR range. In addition, the Jsc of this modified structure improved from 18.84 μA/cm2 to 27.56 μA/cm2 for the visible light. Finally, by using a P25-doped TiO2 layer, the Jsc increased from 0.70 μA/cm2 to 31.12 μA/cm2 for both NIR and visible light, respectively.