ИСТИНА

Recently our group has developed a new strategy of perovskite thin film fabrication using novel reactant compounds, reactive polyiodide melts – the so-called RPM-process [1] that was proved to be applicable to fabrication of high-performance large scale perovskite solar cells [2]. The RPMs can be easily obtained from solid I2 and MAI, exhibit very low melting points and high chemical activity. They are liquid at room temperature, readily react with lead-containing compounds to form the hybrid perovskite CH3NH3PbI3 and do not require the use of any solvent. We found that perovskite can chemically bind iodine to form RPM. Once being formed, RPM acts as a liquid medium that facilitates the recrystallization of perovskite grains. Furthermore, under proper conditions (iodine vapor pressure and time of exposure) this process is reversible and, once excess of iodine is liberated from the system, the target perovskite structure is formed again with no signs of PbI2 or other decomposition products. Using scanning electron microscopy, x-ray diffraction, time-resolved luminescence spectroscopy we showed that iodine treatment is beneficial for the overall quality of perovskite thin films that were fabricated by means of classical solution-based approaches and result in the increase of the average grain size, crystallinity, lifetime of charge carriers. Research was financially supported by the Russian Science Foundation (Project № 18-73-10224).