Band Gap Engineering in NaBiO₃·2H₂O/NaBiO₃·xH₂O Heterostructures for High Photoelectronic Response

High photoelectronic response with a broad spectral range in photoelectric materials is of great importance for photovoltaic and photocatalytic applications. However, the existing photoelectric materials, such as TiO₂ and α-Fe₂O₃, exhibit only high photoelectronic response or only broad spectral response because of the wide band gap limitation of light absorbance or low photogenerated charge separation efficiency. Here, we report NaBiO₃·2H₂O annealed at a given temperature to form NaBiO₃·2H₂O/NaBiO₃·xH₂O heterostructures, which efficiently drives the photogenerated charge separation in a broad spectral range. The best performance of the wide photoelectronic response and high surface photovoltage was obtained in the sample annealed at 130 °C. The high surface photovoltage with a wide spectral range is attributed to the band gap engineering of NaBiO₃·2H₂O/NaBiO₃·xH₂O heterostructures for efficient photogenerated charge separation. These findings regarding the use of optimized NaBiO₃·2H₂O/NaBiO₃·xH₂O heterostructures suggest that fine-tuning the heterostructure of the photoelectric materials is an effective approach for improving the photoelectrical performance in optoelectronic applications.