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Synthesis of CdS thin films were carried out onto glass substrates by chemical bath deposition (CBD) method using CdCl2asCd 2+ and thiourea as S 2-ion source with ammonia as a complexing agent. Influence of bath temperature on structural, morphology and optical properties has been systematically and carefully investigated. XRD analysis revealed that the synthesized CdS films are nanocrystalline having hexagonal structure with (002) preferential orientation. Estimated crystallite size was found in the range 16-32 nm. The UV-Visible spectroscopy analysis showed that the films have high transmission (> 70 %) in visible and NIR region of solar spectrum. Optical band gap was found > 2.3 eV over the entire range of bath temperature studied. The Raman spectra for the CdS films deposited at various bath temperatures shows a continuous shift of 1 LO phonon peak towards higher frequency which suggest the improvement of structural order with increase in bath temperature. The increase in the intensity ratio, 2LO/1LO with bath temperature indicates enhancement of crystallinity of CdS films with increase in bath temperature. The SEM analysis showed that CdS films deposited at various bath temperatures are smooth, homogeneous, and nearly uniform with randomly oriented spherical nanocrystallites.

Herein, we report synthesis of highly stable, Pb-free bismuth iodide, stoichiometric methylammonium bismuth iodide and non-stoichiometric methylammonium bismuth iodide perovskite thin films for photodetector applications.

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