Large grain size CH3NH3PbI3 film for perovskite solar cells with hydroic acid additive

To reduce the defects of perovskite films, various additives are often introduced into the precursor solution. Here, Hydriodic (HI) acid is used as additive in Isopropanol (IPA) solution of methylammonium iodide (MAI) in two-step spin-coated method to obtain high quality MAPbI(3) perovskite film. According to the scanning electron microscope (SEM) image, the grain size of the film increases with the increase of the concentration of HI. When the concentration of addition is 0.004 vol% HI/IPA, the grain size is the largest and the film is the most uniform. In addition, photoluminescence spectra (PL) and Ultraviolet-visible (UV-Vis) absorption spectroscopy show the enhancement of the optical absorption, which also proves the improvement of the film's quality. With the structure of ITO/PTAA/MAPbI(3)/PCBM/Ti/Au, Perovskite Solar Cells (PSCs) were fabricated using MAI solutions with different volume ratios of HI/IPA. The power conversion efficiency (PCE) of the best cell was increased to 18.21% from 16.1%. This study proposes a simple and very effective method of using two-step sequential deposition to produce high-performance PSCs. (C) 2018 Author(s).