Cesium doped H₃PW₁₂O₄₀ nanocrystalline thin films using single step hydrothermal route and its photoelectrochemical properties

The present report focuses on, comparative study of the phosphotungstic acid (H₃PW₁₂O₄₀) (PTA) and cesium (Cs⁺) ion-doped phosphotungstic acid (Cs₃PW₁₂O₄₀) (Cs-PTA) nanocrystalline thin films via facile hydrothermal route. The synthesized PTA and Cs-PTA thin films were characterized for their optostructural, morphological, compositional, electrical, and photoelectrochemical properties. The optical absorption study revealed that direct allowed type of electronic transition with decrease in band gap energy from 3.24 to 2.94 eV as a function of Cs⁺ ion concentration in Cs-PTA thin films. A structural study shows that the synthesized PTA and Cs-PTA thin films were polycrystalline in nature with the formation of a spinel cubic crystal structure. Morphology of the deposited Cs-PTA films illustrates the formation of dense, uniform nanosphere like morphology. The high-resolution transmission electron microscopy (HR-TEM) and selected area electron diffraction (SAED) study confirm the formation of polycrystalline nature of the Cs-PTA thin films. Compositional analysis demonstrates that stoichiometric film formation with valence states of Cs⁺, O²⁻, W⁶⁺, and P⁵⁺ was existed in the Cs-PTA films. The electrical measurement (EC) study shows semiconducting behavior with p-type in nature. Current density–voltage (J–V) measurement demonstrates that Cs-PTA thin films shows boost in PEC performance with photoconversion efficiency of 2.20%.