Finally, using CsI (99, 9%) and PbI 2 (99, 9%), the experiment was repeated for varying thicknesses of CsI (from 200 nm – 500 nm) while PbI 2 is kept constant at 100 nm.New polynitrides containing metastable forms of nitrogen are actively investigated as potential high-energy-density materials. The crystallization of CsPbI 3 was achieved by annealing the film at 100 ℃ for 10 minutes under an air-heated oven. Varying the PbI 2 and CsI thicknesses perfected the CsPbI 3 stoichiometry. Once the required film thickness was achieved, the shutter was closed, and the current was gradually reduced to zero. PbI 2 was evaporated when S1 is opened while S2 is closed, and vice versa for CsI.
CsI thickness was also monitored with a calibrated crystal quartz monitor set with a Z-factor of 1.542 and density of 4.516 g cm -3 for the CsI powder. The monitor was set to have a Z-factor of 1.10 and a density of 6.16 g cm -3 for the PbI 2 powder. With the aid of a thermocouple and quartz crystal monitor, mounted on the same level as the substrates, the film temperature and thickness were constantly monitored. The turbo-pump was activated to exhaust air from the evaporation chamber until a vacuum pressure of 2×10 -5 mBar was reached. The metallic coils were electrically separated by two switches S1 and S2 connected to an external power supply circuit, as illustrated in Figure 3.2. The crucibles were placed on two separate heating coils for evaporation inside the chamber. Precursor powders were introduced into the chamber using separate boron nitride crucibles labeled C1 and C2, with C2 containing CsI and C1 containing PbI 2. CsI and PbI 2 precursors were used as received (from Sigma-Aldrich). Subsequently, c-TiO 2 thin films were annealed at 450 ℃ for an hour and characterized.įigure 3.2 displays the SPVD schematic for CsPbI 3.The thin films of CsPbI 3 were grown on cleaned and treated substrates (as described in section 3.3).
Substrates were then allowed to cool to room temperature (25 ℃) naturally. For this method, a spray pressure of 3 kPa was employed, air as a carrier gas, a 20 cm nozzle to substrate diameter and a 0.5 mm nozzle diameter, and with rapid sweeps, every 60s and 15s delays between them. The thin films were formed by spraying the c-TiO 2 solution mixture on the preheated substrates, using the spray pyrolysis technique, as illustrated in Figure 3.1. The hotplate was slowly warmed to prevent thermal strain on the glass substrates as the desired temperature of 250 ℃ was reached. Then, the substrates were placed on a hotplate.
#CAESIUM NITRIDE FREE#
To keep some FTO areas free of c-TiO 2 coverage, the edge portions of the substrates were covered with thermal tape. The mixture was stirred at room temperature (25 ℃) until it produced a colorless homogeneous solution. The solution of compact -titanium dioxide (c-TiO 2) thin films was prepared from a mixture of 0.5M titanium tetra-isopropoxide (TTIP) (Sigma Aldrich, purity N97.0%), and 50 mL ethanol (Sigma-Aldrich Reagent) solutions. The solar cells’ efficiency of 4% showed no dependency on the thickness of the CsI layer. The materials were subsequently used to fabricate perovskite solar cells. The thin films were characterized using XRD, SEM, and UV-vis spectroscopy to determination of the band gaps. The dataset reports on the synthesis and characterization of titanium dioxide thin films using the spray pyrolysis method and fabrication of CsPbI 3 thin film using the sequential physical vapor deposition method.
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