Optimizing concurrent extension of near-infrared and ultraviolet light harvesting of dye sensitized solar cells by introducing sandwich-nanostructured upconversion-core/inert-shell/downconversion-shell nanoparticles

Simultaneous realization of upconversion (UC) and downconversion (DC) processes in a single unit provides unique opportunities of photons utilization throughout a broad spectral range for dye-sensitized solar cells (DSSCs). Yet, the existence of cross relaxation quenching effect in UC/DC interface causes a low synergistic effect. Here, we propose a strategy of embedding an inert layer to spatially separate active UC and DC layers at precisely defined thickness. The construction of sandwich-nanostructured NaYF4:20%Yb3+,2% Er3+ @NaLuF4@NaYF4:15%Eu3+ allows the elimination of detrimental cross relaxation quenching, implementing optimal synergistic effect of UC/DC system and further extending simultaneous near-infrared (NIR) and ultraviolet (UV) absorption of DSSC devices to the most extend. By incorporating the sandwiched UC-core/inert-shell/DC-shell nanoparticles into the TiO2 photoanode of DSSCs, the increased photon-electron conversion efficiency (PCE) of 7.87% was obtained mainly by the increased photocurrent of 14.93 mA/cm(2) due to the concurrent NIR and UV light harvesting enhancement (PCE = 6.73%, J(sc)= 11.91 mA/cm(2) for the control cell without the sandwiched spectral layer), thus, showing a noticeable PCE enhancement ratio of similar to 16.94%. This work provides a promising strategy to integrate various photons processes in one single unit and broaden spectral respond toward high-efficiency solar cell systems.