Figure 2: Acid–base reacted colloidal solution. | Nature Communications

Figure 2: Acid–base reacted colloidal solution.

From: Nonstoichiometric acid–base reaction as reliable synthetic route to highly stable CH3NH3PbI3 perovskite film

Figure 2

(a) Tyndall effect using 532 nm laser suggests the colloidal behaviour of starting 1.0 M PbI2 and 1.0 M, 2.0 M HPbI3, control 1:1 combination of 1 M CH3NH3I:PbI2 precursor and acid–base precursors prepared via adding 0.2 ml CH3NH2 ethanol solution into 0.5 ml of 1.5 M HPbI3 solution. (b) Ultraviolet spectra of starting PbI2 and HPbI3 precursors, as well as control 1:1 combination of 1 M CH3NH3I:PbI2 precursor. Array indicates redshift after full iodine coordination. (c) Colloidal variation of the acid–base precursors prepared by stepwise addition of 25-μl CH3NH2 ethanol solution into 0.5 ml of 2M HPbI3 (from left to right, 0 to 400 μl, white dash line lies after 300 μl). (d) Absorption spectrum variation of the acid–base precursors prepared by stepwise addition of 20-μl CH3NH2/ethanol solution into 0.3 ml of 1 M HPbI3. (e) Absorption spectrum variation of 0.3 ml of 1 M control 1:1 CH3NH3I:PbI2 precursors through stepwise addition of 20-μl CH3NH2/ethanol solution. The spikes at around 335 nm are caused by the precipitate after adding too much CH3NH2/ethanol solution.

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