Polypyrrole-bismuth tungstate/polypyrrole core-shell for optoelectronic devices exhibiting Schottky photodiode behavior.

A polypyrrole-bismuth tungstate (Ppy-BiWO) core-shell nanocomposite (n-type material) has been developed on a layered Ppy (p-type) base as an efficient light-capturing material exhibiting photodiode behavior. This device demonstrates promising sensitivity for light sensing and captures across a broad spectral range, from near IR to UV. The BiWO/Ppy nanocomposite boasts an optimal bandgap of 2.0 eV, compared to 3.4 eV for Ppy and 2.5 eV for BiWO. The crystalline size of the core-shell composite is approximately 21 nm, emphasizing its photon absorption capabilities. The composite particles, around 100 nm in length, feature a highly porous morphology that effectively traps incident photons. The performance of this optoelectronic device is evaluated using current density (J) measurements under light (J) and dark (J) conditions. In darkness, the n-p type semiconductor exhibits limited current with a Jo of -0.22 mA cm at 2.0 V. When exposed to white light, the Ppy- BiWO/Ppy device generates hot electrons, achieving a J value of 1.1 mA/cm at 2.0 V. It shows a superior responsivity (R) of 6.6 mA/W at 340 nm, gradually decreasing to 6.3 mA/W at 440 nm and 4.2 mA/W at 540 nm, indicating high sensitivity across the UV-Vis spectrum. At 730 nm, the R-value is 2.6 mA/W, highlighting its sensitivity in the near IR region. Additionally, at 340 nm, the device achieves a detectivity (D) value of 0.15 × 10¹⁰ Jones, which decreases with longer wavelengths to 0.14 × 10¹⁰ Jones at 440 nm, 0.9 × 10⁹ Jones at 540 nm, and 0.63 × 10⁹ Jones at 730 nm. With its great stability, low cost, easy fabrication, and potential for mass production, this optoelectronic light sensor and photodiode device holds significant promise for industrial applications as a highly effective optoelectronic device.