Bismuth Chalcogenide Nanoparticles for Eco-Friendly Optoelectronic Devices

Bismuth-based compounds (Bi₂X₃, where X = O, S, Se, Te) are promising materials for optoelectronic and solar energy applications. They have the potential to replace toxic lead in hybrid perovskites [1-3]. Hybrid lead perovskites (MAPbI₃), when degraded, can release toxic Pb²⁺ into the environment, posing serious risks to human health and ecosystems. To overcome this, lead-based perovskites can be replaced with bismuth-based chalcohalides (MABiXI₂, X = O, S, Se, Te), which offer similar properties with lower toxicity and improved stability. Bismuth chalcohalides can be synthesized using bismuth chalcogenides. In this study, we discuss the synthesis and optoelectronic characterizations of bismuth chalcogenide Bi₂X₃ nanoparticles. They were synthesized via a simple solvothermal method and characterized using structural, optical, and electrical techniques. X-ray diffraction confirmed high-purity nanoparticles with hexagonal, orthorhombic, or tetragonal crystal structures and good crystallinity. Crystallite sizes, calculated using the Scherrer equation, ranged from 15 to 20 nm. Raman spectroscopy revealed distinct vibrational modes corresponding to each phase. Temperature-dependent resistivity measurements confirmed semiconducting behavior, with Bi₂Te₃ showing the highest resistivity and activation energy. The direct band gaps of bismuth chalcogenides were measured in the range of 1.7 eV to 2.9 eV. Electrical analysis based on the Poole–Frenkel model provided insights into the energy barrier that electric charge carriers have to cross to move in the material and also the dielectric constant. These results highlight the potential of Bi₂X₃ nanoparticles in optoelectronic and solar energy devices.