Synthesis and photovoltaic response study of magnetic Bi ₂ Te ₃ @Fe ₃ O ₄ nanocomposites

Abstract In this study, we report the synthesis of Bi 2 Te 3 @Fe 3 O 4 nanocomposites using a two-step hydrothermal method and their photovoltaic applications. The coexistence of both Bi 2 Te 3 and Fe 3 O 4 phases in the nanocomposite form was confirmed through Rietveld refinement of x-ray diffraction analysis, Field emission scanning electron microscopy, and Transmission electron microscopy EDX studies. By identifying their respective vibrational modes, Raman spectral analysis also validates the successful formation of Bi 2 Te 3 @Fe 3 O 4 nanocomposite. The optical absorption spectra, obtained via UV–vis spectroscopy, revealed band gaps of 0.92 eV for pristine Bi 2 Te 3 and 1.25 eV for the Bi 2 Te 3 @Fe 3 O 4 nanocomposites. Vibrating sample magnetometry (VSM) analysis confirmed the emergence of superparamagnetic characteristics in the nanocomposites, while Bi 2 Te 3 exhibits diamagnetic behaviour. Photovoltaic measurements under dark and illuminated conditions revealed that the Bi 2 Te 3 /Si junction delivered an I sc of 0.13 mA, a V oc of 0.045 V, and a power conversion efficiency (PCE) of 0.007%. In contrast, the Bi 2 Te 3 @Fe 3 O 4 /Si nanocomposite showed a significant improvement, with I sc and V oc rising to 0.69 mA and 0.32 V, respectively, resulting in an enhanced PCE of 0.45%. This enhancement is attributed to better light absorption and more efficient charge separation, with Fe 3 O 4 nanoparticles acting as electron acceptors at the interface.