Regular Article Constructing efficient mixed-ion perovskite solar cells based on TiO 2 nanorod array Longkai Yang a , Xin Wang a , Xianmin Mai b,⇑ , Tan Wang c , Chao Wang d,e , Xin Li a,⇑ , Vignesh Murugadoss d,f , Qian Shao g , Subramania Angaiah f,⇑ , Zhanhu Guo d,⇑ a Pen-Tung Sah Institute of Micro-Nano Science and Technology, Xiamen University, Xiamen 361005, China b School of Urban Planning and Architecture, Southwest Minzu University, Chengdu 610041, China c College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China d Integrated Composites Laboratory (ICL), Department of Chemical & Biomolecular Engineering, University of Tennessee, Knoxville, TN 37996, United States e College of Materials Science and Engineering, North University of China, Taiyuan 030051, China f Electrochemical Energy Research Lab, Centre for Nanoscience and Technology, Pondicherry University, Puducherry 605 014, India g College of Chemical and Environmental Engineering, Shandong University of Science and Technology, Qingdao 266590, China graphical abstract article info Article history: Received 30 June 2018 Revised 17 August 2018 Accepted 12 September 2018 Available online 14 September 2018 Keywords: TiO 2 Nanorod array Mixed-ion Perovskite solar cell abstract Oriented TiO 2 nanorod array (TiO 2 NA) is very attractive in the fields of halide perovskite solar cells (PSCs) due to its fewer grain boundaries and high crystallinity for effective charge collection. The optimization of TiO 2 nanostructures has been proved to be an effective approach for efficient PSCs. On the other hand, tuning the crystallization of perovskite films on top of the TiO 2 NA is very important for efficient TiO 2 - NA based PSCs. Herein, scanning electron microscopy (SEM) and X-ray powder diffraction (XRD) were used to study the crystallization of different mixed-ion Cs 0.1 (FA 0.83 MA 0.17 ) 0.9 Pb(I 0.83 Br 0.17 ) 3 perovskite (in which MA = CH 3 NH 3 + , and FA = CH(NH 2 ) 2 + ) films, from different perovskite precursor concentrations, on the TiO 2 nanorod arrays. A mechanism was proposed to reveal the inherent connection between the precursor concentration and the crystallite growth of the perovskite film prepared with anti- solvent quenching process. Meanwhile, both faster charge separation at perovskite/TiO 2 NA interface and longer charge transport were observed on thicker perovskite film with larger grains, revealed by the time-resolved method. However, atomic force microscopy (AFM) results indicated that too thick per- ovskite film impaired the charge collection owing to the increased recombination. By balancing the charge collection and film thickness, highly efficient PSCs were prepared with a champion power https://doi.org/10.1016/j.jcis.2018.09.045 0021-9797/Ó 2018 Elsevier Inc. All rights reserved. ⇑ Corresponding authors. E-mail addresses: maixianmin@foxmail.com (X. Mai), lixin01@xmu.edu.cn (X. Li), a.subramania@gmail.com (S. Angaiah), zguo10@utk.edu (Z. Guo). Journal of Colloid and Interface Science 534 (2019) 459–468 Contents lists available at ScienceDirect Journal of Colloid and Interface Science journal homepage: www.elsevier.com/locate/jcis