Intrinsic formamidinium tin iodide nanocrystals by suppressing the Sn(IV) impurities

Abstract

All glassware was dried at 130 C for at least an hour and put directly inside the glovebox. Flask was loaded with 0.15 g (0.4 mmol) SnI2 (purified by sublimation and washing), 0.4 mL TOP, 9.6 mL dried Dowtherm A, 80 uL distilled OLAm and connected to a Schlenk line without exposing materials to air. All parts outside the flask were purged three times with N2. Then the flask was heated to 80 C under N2 and 0.8 ml of dried FAol solution was injected. The reaction mixture was quenched by an ice bath immediately after injection and brought to the glovebox for washing without exposing NCs to air. The crude solution was centrifuged at 12.4 krpm for 10 minutes. The precipitate was redispersed in 1 ml toluene and centrifuged at 3 krpm for 2 minutes keeping only the supernatant. Obtained NCs were precipitated by anhydrous acetonitrile and redissolved in toluene. Characterization4.1 UV/vis/IR absorption spectra were collected using a Jasco V670 spectrometer.4.2 Room-temperature steady-state photoluminescence (PL) spectra were acquired on the Fluoromax-4 Horiba spectrofluorometer equipped with a photomultiplier tube (PMT) as a detector and 150 W Ozone-free xenon arc lamp as a light source. All spectra were corrected for the detector sensitivity. Time-resolved emission spectra (TRES)were acquired with a PicoQuant FluoTime 300 spectrometer that was equipped with a TimeHarp 260 PICO counting unit. An excitation wavelength of 355 nm was utilized (from a frequency-tripled, picosecond Nd:YAG laser by PicoQuant).4.4 Time-resolved PL spectra were taken from TRES data for wavelengths corresponding to PL maximum. 4.5 Absolute photoluminescence quantum yield (PL QY) of NCs was acquired from colloidal solutions using the Quantaurus-QY Absolute PL quantum yield spectrometer (C11347-11; Hamamatsu) equipped with an integrating sphere. Excitation source emission wavelength was set to 450 nm.