Synthesis Strategy of Cs2SnI6 Perovskite by Modified Hot Injection Method and Its Potential Application for Optoelectronic Device Hilarius Donatus Hun, Difa Ayatullah Muthmainnah, Hawinda Restu Putri, Setiya Rahayu, and Priastuti Wulandari*
Physics of Magnetism and Photonic Research Division, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jl. Ganesha 10 Bandung 40132, West Java, Indonesia
*pwulandari[at]itb.ac.id
Abstract
In recent years, the easy and environmentally friendly synthesis of lead-free perovkite materials has become a competitive topic for researchers especially related to the application in solar energy harvesting technology. Lead-free perovskite using tetravalent tin (Sn4+, Cs2SnI6) has attracted much attention compared to divalent tin (Sn2+, CsSnI3) because it is more stable and can be synthesized without using a glove box. The synthesis of this type of perovskite is often carried out using solution-based techniques because it allows for control of the size and shape of the perovskite. Previously, this type of perovskite was widely synthesized using a simple chemical solution method by reacting CsI and SnI4 at room temperature. However, this technique cannot control the size and shape of the perovskite. In the hot injection method, the size and shape of the resulting nanocrystals can be controlled by varying the reaction time between Cs-Oleate and the SnI4 complex at high temperatures.
The synthesis of Cs2SnI6 perovskite using the hot injection method is usually carried out in a low-pressure environment with an inert gas flowing. In this study, we synthesized Cs2SnI6 perovskite using the hot injection method with only N2 gas flowing. As a result, we obtain a dark brown paste precipitate that is green when irradiated with a 408 nm laser. Then we purified this precipitate using toluene and hexane (1:1). Furthermore, we performed characterization of Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Ultraviolet-Visible Spectroscopy (UV-Vis), Photoluminescence Spectroscopy (PL), Fourier Transform Infrared (FTIR), and Raman spectroscopy.
The SEM results show that the Cs2SnI6 perovskite has a spherical shape with an average diameter of about 0.70 μ-m for the unpurified sample and 0.84 μ-m for the purified sample. The XRD results show that the formed Cs2SnI6 perovskite has a cubic crystal structure for both unpurified and purified samples. In addition, the results of chemical characterization with FTIR and Raman spectroscopy show differences in vibration frequencies for the samples without purification and after purification due to the influence of the solvent and ligands involved. The results of optical characterization with UV-Vis spectroscopy and Photoluminescence show two specific peaks in samples without purification and purification. However, there is found the shifted in the absorbance peak towards a larger wavelength (red shift).
Keywords: Lead-free perovskite, Cs2SnI6 synthesis, Hot injection technique, Purification effects
