Modification of compact TiO_(2) layer by TiCl_(4)-TiCl_(3) mixture treatment and construction of high-efficiency carbon-based CsPbI_(2)Br perovskite solar cells

In the construction of high performance planar perovskite solar cells(PSCs),the modification of compact TiO_(2) layer and engineering of perovskite/TiO_(2) interfaces are essential for efficient electron transfer and retarded charge recombination loss.In this work,a facile and effective strategy is developed to modify the surface of compact TiO_(2) layer by TiCl_(4)-TiCl_(3) mixture treatment.Compared with conventional sole TiCl_(4),the TiCl_(4)-TiCl_(3) treatment takes the advantage of accelerated and controlled hydrolysis of TiCl_(3),therefore TiO_(2) with dominating anatase phase and moderate roughness is obtained to facilitate the growth of CsPbI_(2) Br perovskite layer with high quality.Furthermore,the oxidation-driven hydrolysis of TiCl_(3) component results in surface Cl doping that facilitates interfacial electron transfer with retarded recombination loss.The average power conversion efficiency(PCE) of carbon-based CsPbI_(2) Br planar PSCs based on TiCl_(4)-TiCl_(3) treatment increases to 14.18% from the intial 13.04% based on conventional sole TiCl_(4) treatment.The champion PSC exhibits a PCE of 14.46%(V_(oc)=1.28 V,J_(sc)=14.21 mA/cm^(2),and FF=0.794),which is one of the highest PCEs for carbon-based CsPbI_(2) Br PSCs.