The Role of Thickness Control and Interface Modification in Assembling Efficient Planar Perovskite Solar Cells

Perovskite solar cells (PSCs) have achieved tremendous success within just a decade. This success is critically dependent upon compositional engineering, morphology control of perovskite layer, or contingent upon high-temperature annealed mesoporous TiO(2), but quantitative analysis of the role of facile TiCl(4) treatment and thickness control of the compact TiO(2) layer has not been satisfactorily undertaken. Herein, we report the facile thickness control and post-treatment of the electron transport TiO(2) layer to produce highly efficient planar PSCs. TiCl(4) treatment of TiO(2) layer could remove the surface trap and decrease the charge recombination in the prepared solar cells. Introduction of ethanol into the TiCl(4) aqueous solution led to further improved open-circuit voltage and short-circuit current density of the related devices, thus giving rise to enhanced power conversion efficiency (PCE). After the optimal TiCl(4) treatment, PCE of 16.42% was achieved for PSCs with TiCl(4) aqueous solution-treated TiO(2) and 19.24% for PSCs with TiCl(4) aqueous/ethanol solution-treated TiO(2), respectively. This work sheds light on the promising potential of simple planar PSCs without complicated compositional engineering and avoiding the deposition and optimization of the mesoporous scaffold layer.