Dual-sized TiO2 nanoparticles as scaffold layers in carbon-based mesoscopic perovskite solar cells with enhanced performance

Dual-sized TiO2 scaffold layer was successfully prepared by dispersing appropriate 100 nm-sized TiO2 nanoparticles into conventional TiO2 scaffold layer composed of 25 nm-sized TiO2 nanoparticles, and then applied to carbon-based mesoscopic perovskite solar cells. Compared with conventional TiO2 scaffold layer, the dual-sized TiO2 scaffold layer not only exhibits higher light-harvesting efficiency due to the better light scattering ability of 100 nm-sized TiO2 nanoparticles, but also shows significantly improved infiltration of perovskite into the scaffold layer because of the larger voids formed within the dual-sized TiO2 scaffold layer. These merits lead to much higher short-circuit photocurrent density and thus power-conversion efficiency. The average short-circuit photocurrent density and power-conversion efficiency of the carbon-based mesoscopic perovskite solar cell employing dual-sized TiO2 scaffold layer with an 14.4% mass fraction of 100 nm-sized TiO2 nanoparticles are 19.31% and 18.57% higher than those of the cell based on conventional TiO2 scaffold layer. The power-conversion efficiency is further improved to 11.69% by optimizing the thickness of the dual-sized TiO2 scaffold layer. The combination of superior light harvesting capability and complete perovskite infiltration make the dual-sized TiO2 film a good candidate as the scaffold layer for carbon-based mesoscopic perovskite solar cells.