Recrystallization and grain growth by intense pulsed light with mixed solvent annealing for efficient perovskite solar cells

A novel processing technique using a two-step intense pulsed light (IPL) with a mixed solvent annealing method to increase the grain size of perovskite film was investigated. Three annealing methods [thermal, IPL, and IPL with mixed solvent] were contrasted in the perovskite recrystallization procedure. The grain size of the recrystallized perovskite films according to the composition of the mixed solvent [a mixed solvent of chlorobenzene (a non-solvent) and isopropyl alcohol (a solvent)] was determined through atomic force microscope and X-ray diffraction (XRD), and compared with those of produced using the traditional annealing method (thermal and IPL). The surface roughness of the films made with IPL with mixed solvent was significantly increased compared to previous techniques. The grain size of the perovskite films was obtained through the analysis of scanning electron microscope images; the average grain sizes of thermal, IPL, and IPL with mixed solvent annealing were 217, 351 and 381 nm, respectively. The grain orientation of the formed perovskite films was investigated through XRD analysis, and the alignment of the grains could be discovered through the peak intensity ratio analysis of these grain planes. Through this structural and spatial alignment analysis, it was found that the new annealing process produces a larger (converted to monocrystalline-like grains) and anisotropic (normal to the substrate plane) perovskite grains than the traditional annealing method. The power conversion efficiency of the device fabricated in an ambient condition by the new annealing approach was 11.39 ± 0.36% (maximum value was 11.86%), which was nearly 8% higher than that of the device fabricated by the traditional annealing method. • Developed a novel process for perovskite recrystallization. • Used a combined process of mixed solvent and intense pulsed light annealing. • Formed highly oriented anisotropic large perovskite grains.