Effect of macropores in titanium dioxide layer on the enhancement of photovoltaic conversion efficiency of long-persistence-phosphor enhanced dye-sensitized solar cells

Mesoporous TiO2 (m-TiO2) have been often employed to improve the photovoltaic conversion efficiencies (PCEs) of the dye-sensitized solar cells (DSSCs). While when incorporated with a long-persistence-phosphor (LPP) layer, only a limited PCE enhancement was obtained for the resultant DSSCs. This is mainly due to that little incident sunlight can transport through the solid m-TiO2 photoanode films and then enter and excite the LPP layer. Here in this work, tunable amount of macropores were introduced into hierarchically porous TiO2 (h-TiO2) using polyvinylpyrrolidone (PVP) as pore-forming agent. As a result, the optimized DSSCs with h-TiO2/LPP photoanodes show the highest PCE of 8.05%, which is improved by 29.00% and 14.51%, compared to those with m-TiO2 and m-TiO2/LPP ones, respectively. Series of analysis indicates that the macropores benefit the transmission of incident sunlight through the h-TiO2 layer and reduce the light reflection at the interface of h-TiO2/LPP. Furthermore, the carbon-doping in TiO2 caused by PVP shifts up the Fermi level of TiO2 and the interface of h-TiO2/LPP enhances the separation of photo-generated carriers, both of which increase the open circuit voltage of the DSSCs. In addition, the DSSCs with h-TiO2-8/LPP photoanodes can well work in dark with a real PCE of 57.37%. (C) 2022 Elsevier B.V. All rights reserved.