ИСТИНА

Reactive polyiodide melts (RPM) are liquid polyiodides which can be readily prepared by mixing powders of I2 with organic halides (MAI, FAI, GuaI). The reaction proceeds instantly at room temperature and results in a highly-viscous ionic liquid. These compounds, namely, CH3NH3I3+x and HC(NH2)2I3+x, are liquid at room temperature in a large range of precursors ratios [1]. The RPM has been recently found to be a highly corrosive decomposition product which forms under sunlight and cause degradation of perovskite solar cells components, including spiro MeOTAD and gold electrode [2]. On the contrary, an extremely high reactivity of the RPM is an important advantage of such compounds as they easily oxidize metallic Pb and lead compounds (e.g. PbI2, PbO) thus forming perovskite according to the following reaction: MAI3 + Pb → MAPbI3. Therefore, the RPM open up a new formation strategy of hybrid lead halide perovskites using the RPM. We present that perovskite crystals and thin films can be easily obtained through the direct reaction between reactive polyiodide melts and metallic lead. Due to its unique composition the RPM acts simultaneously as a liquid medium and a highly reactive precursor that swiftly converts metallic lead into perovskite. This new approach allows fabrication of high quality polycrystalline perovskite films with micron-size grains without use of solvents and heating. The perovskite solar cells made via this approach yield a solar to electric power conversion efficiency (PCE) of over 12% even without optimization of the film deposition procedure. We demonstrate applicability of this method for the fabrication of highly uniform perovskite films with micron-size grains over large substrates of 10x10 cm2 and 20x30 cm2, including flexible supports. The proposed strategy has a high potential for industrial scale mass-production of perovskite modules including roll-to-roll manufacturing on flexible substrates, because the initial lead thin films can be easily deposited in a highly controlled way by various methods, such as evaporation, sputtering, electrochemical deposition, etc. We also demonstrate that mixed perovskites MAxFA1-xPbI3-xBrx can be easily obtained using the RPM with various compositions. In particular, single-phase MA-stabilized FAPbI3 films with long charge carrier lifetimes were obtained. References [1] A.A. Petrov, N.A. Belich, A.Yu. Grishko, et al. Mater. Horiz. (2017), 625–632. [2] N.N. Shlenskaya, N.A. Belich, M. Grätzel, E.A. Goodilin, A.B. Tarasov, J. Mater. Chem. (2018), 1780–1786.