Photonic sintering of a ZnO nanosheet photoanode using flash white light combined with deep UV irradiation for dye-sensitized solar cells

The present report details research work on the photonic sintering of ZnO nanosheets (ZnO NSs), which were synthesized via a solid-state synthesis method. The sintering was performed using flash white light (FWL) combined with deep UV irradiation (photonic sintering) under ambient conditions at ultra-high speed, which is a superior process over the conventional thermal-sintering process. Furthermore, the application of this method was demonstrated in dye-sensitized-solar cells (DSSCs), where a power conversion efficiency (PCE) of 2.9% was achieved when the photoanode was annealed using photonic sintering with a FWL of 20 J cm^-2 combined with deep UV irradiation of 30 mW cm^-2 irradiation power. This PCE is higher than that of the pristine ZnO NSs (PCE = 1.5%) and of the thermally sintered ZnO NS photoanode (PCE = 2.0%). The superior performance of the dye cell with the photonic-sintered ZnO NSs is attributed to the better interconnection, higher effective electron diffusion coefficient (D_n), higher electron diffusion length (L_n) and a higher amount of dye loading than that of the pristine ZnO NS photoanode. The improved PCE suggests that the photonic-sintering method, as well as being extremely simple, is highly effective and enables a fast annealing for photoanodes in DSSCs and could be particularly beneficial for low-temperature-based solar cells.