Inorganic perovskite
materials are possible candidates for conversion
of solar energy to electrical energy due to their high absorption
coefficient. Perovskite solar cells (PSCs) introduced a new type of
device structure that has attention due to better efficiencies and
interest in PSCs that has been increasing in recent years. Halide
perovskite materials such as CsPbIBr2 show remarkable optical
and structural performance with their better physical properties.
Perovskite solar cells are a possible candidate to replace conventional
silicon solar panels. In the present study, CsPbIBr2 perovskite
materials’ thin films were prepared for light-absorbing application.
Five thin films were deposited on the glass substrates by subsequent
spin-coating of CsI and PbBr2 solutions, subsequently annealed
at different temperature values (as-deposited, 100, 150, 200 and 250
°C) to get CsPbIBr2 thin films with a better crystal
structure. Structural characterizations were made by using X-ray diffraction.
CsPbIBr2 thin films were found to be polycrystalline in
nature. With increasing annealing temperature, the crystallinity was
improved, and the crystalline size was increased. Optical properties
were studied by using transmission data, and by increasing annealing
temperature, a small variation in optical band gap energy was observed
in the range of 1.70–1.83 eV. The conductivity of CsPbIBr2 thin films was determined by a hot probe technique and was
found to have little fluctuating response toward p-type conductivity,
which may be due to intrinsic defects or presence of CsI phase, but
a stable intrinsic nature was observed. The obtained physical properties
of CsPbIBr2 thin films suggest them as a suitable candidate
as a light-harvesting layer. These thin films could be an especially
good partner with Si or other lower band gap energy materials in tandem
solar cells (TSC). CsPbIBr2 material will harvest light
having energy of ∼1.7 eV or higher, while a lower energy part
of the solar spectrum will be absorbed in the partner part of the
TSC.
The development of cost-effective and nontoxic thin film materials is vital for fabrication of solar cells. We are presenting a combinatorial synthesis approach (CSA) for the deposition of chalcogenide Sn-Bi-S graded thin films by thermal evaporation. Post-deposition thermal annealing in the temperature range of 200-500°C in an argon atmosphere has been carried out for the Sn-Bi-S thin films. The effect of annealing treatment and initial composition on the structural properties of the Sn-Bi-S graded thin films was studied by using energy-dispersive X-ray spectroscopy, X-ray diffraction (XRD), and Raman spectroscopy. XRD measurements showed that the thin films were grown in polycrystalline structure. Different microstructural parameters such as crystallite size, dislocation density, and microstrain were estimated after postdeposition thermal treatment and found annealing temperature dependent. From the transmission spectra the estimated optical band gap energy values were found in the range 1.27-1.43 eV for the (Sn/Bi) molar ratio of 2.18-0.67 in a typical sample annealed at 400°C. Photoconductivity response was determined for incident light of wavelength 300-1100 nm and was observed to be annealing temperature and Sn/Bi molar ratio dependent. Photoconductivity was also noted to depend upon the Sn/Bi molar ratio with Sn-rich samples giving the strongest response. Sn-rich compositions also showed p-type conductivity over the temperature range of 350-400°C. These findings show that the CSA has potential for the screening of high-quality Sn-Bi-S thin films.
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