Abstract
Lead halide thin films, such as lead iodide (PbI2) and lead chloride (PbCl2), are used as precursor films for perovskite preparation, which is frequently achieved by vacuum thermal evaporation but rarely by the low-pressure chemical vapor deposition (CVD) method. Here, we report on the deposition of PbI2 and PbCl2 thin films on glass substrates by employing the low-pressure CVD method. The effect of the substrate temperature on the structure and morphology of the lead halide films is investigated. Crystalline films were realized for both lead halides, with PbI2 films showing high texture compared to the reduced texture of the PbCl2 films. Large lateral grain sizes were observed for the PbI2 films with a flat platelet grain morphology and an average grain size up to 734.2 ± 144.8 nm. PbCl2 films have columnar grains with an average grain size up to 386.7 ± 119.5 nm. The PbI2 films showed a band gap of about 2.4 eV, confirming its semiconducting properties, and the PbCl2 had a wide band gap of 4.3 eV, which shows the insulating properties of this material.
Highlights
Lead halide (PbX2 ) thin films have been studied extensively as precursors for the recently discovered organic–inorganic halide perovskite thin film absorbers for photovoltaic application [1,2,3,4,5,6].The deposition of PbX2 (X = iodine, chlorine, or bromine halide anions) is usually performed in the first step of the sequential two-step deposition of hybrid perovskite thin films [3,4,5,6]
This highly intense (001) peak demonstrates that these PbI2 films are highly textured as there there appears to be no other family of planes in the X-ray diffraction (XRD) pattern such as the (110) [8]
This may be due to the improved crystallinity of the film due to higher higher deposition substrate temperature or a greater film thickness compared to its low-temperature deposition substrate temperature or a greater film thickness compared to its low-temperature counterpart
Summary
The deposition of PbX2 (X = iodine, chlorine, or bromine halide anions) is usually performed in the first step of the sequential two-step deposition of hybrid perovskite thin films [3,4,5,6]. Due to the high atomic weight (ZPb = 82, ZI = 53) of PbI2 , it is applied as a good absorber of X-rays [7,8,9,10]. It has been used as a stable nuclear radiation detector that is able to detect X-rays and Gamma rays [9,10].
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