Post-treatment of Nb2O5 compact layer in dye-sensitized solar cells for low-level lighting applications

Introduction of an ultrathin compact layer in dye-sensitized solar cells (DSSCs) can improve the cell efficiency under standard one sun illumination (> 100,000 lx). Herein, an ultrathin Nb2O5 layer is deposited on the TiO2-coated photoanode using a facial dip-coating method and its effects on the cell efficiency under a low level of light intensity (300-6000 lx) is studied. The results show that the ultrathin Nb2O5 layer helps the DSSCs to improve their power conversion efficiency (PCE) through different ways under standard one sun and low power illuminations. Under strong one sun illumination, the PCE of DSSC is improved by improving the short-circuit current density (J(SC)) which can be attributed to an increment of the surface area of photoanode for more dye adsorption and the blocking effect of Nb2O5. Under low power illumination, the introduction of Nb2O5 blocking layer improves the fill factor by effectively suppressing the charge recombination on the photoanode.