Hydriodic Acid: Regeneration of Oxidized Solutions

Investigation on the properties of hybrid CH3NH3SnxI3 (0.9 ≤ x ≤ 1.4) perovskite systems

“…To avoid the Sn-oxidation during the preparation with corresponding formation of purple I 3À species, 3.5 mL H 3 PO 2 solution (hypophosphorous acid, 50 wt%, Fisher Scientific, Loughborough, United Kingdom) was added in solution (9.0 mL) during heating up. 16,17 After cooling down the solution to room temperature, the crystallized black powders were separated from the mother liqueur and washed with 2propanol, then with di-ethyl-ether, and finally with toluene. The powders did not optically reveal any changes even after days under ambient conditions.…”

Investigation of Methylammonium Tin Strontium Bromide Perovskite Systems

“…In particular, Sn(CH 3 COO) 2 (tin(II) acetate, Alfa Aesar), HBr (47% wt, hydrobromic acid, Alfa Aesar), CH 3 NH 2 (40% wt aqueous solution, methylamine, Alfa Aesar), SrCO 3 (strontium carbonate, Aldrich) were used as delivered. A typical preparation process was carried out by adding a corresponding amount of CH 3 NH 2 into 18 mL concentrated HBr aqueous solutions which contained 10 mmol of Sn-and Sr-ions (in order to have MA: (Sn + Sr) = 1: 1 molar ratio) and heated up to T = 110 • C. In order to avoid the Sn(II) oxidation into Sn(IV), 7.0 mL H 3 PO 2 solution (hypophosphorous acid, 50% wt, Fischer Scientific, UK) was added into starting solution during the heating step up to 110 • C. 11,12 After cooling down the solution to room temperature, the prepared orange powders were separated by filtration, washed with 2-propanol, then with diethyl-ether again and finally with toluene. After drying out under ambient conditions, the samples were annealed at T = 150 • C for t = 8 h in a tubular quartz oven under flowing nitrogen.…”