Topological insulators (TI) with their rapid electron dynamical behavior under light stimulation and broad-spectrum absorbance have been shown to have interesting uses in next generation optoelectronics. In this work, the characteristics and functionality of a newly n-Bi₂Te₂Se/p-Bi₂Te₃ (TI/TI) vertical hetero-junction fabricated by using thermal evaporation process as an effective photodetector are examined. The fabricated self-powered heterojunction photodetector resulted in an ultralow Noise equivalent power (NEP) of 1.95×10^-14 WHz^-1/2 achieved at 661.24 µW/cm² under 1300 nm illumination, an ultrahigh photoresponsivity of 429.95 A/W, and a high detectivity of 3.57×10¹² Jones. Furthermore, the computation study of Bi₂Te₂Se/Bi₂Te₃ heterostructure was estimated using first principle based on density functional theory (DFT). The electronic and optical properties of single quintuple layer (QL) of Bi₂Te₂Se, Bi₂Te₃ and there heterostructure were calculated. At gamma point, the calculated value of bandgap of Bi₂Te₂Se, Bi₂Te₃ and Bi₂Te₂Se/Bi₂Te₃ are 0.32, 0.26 and 0.106 eV respectively. Further, for optical properties, the real and imaginary part of dielectric function of these topological materials and their heterostructure was calculated by using random phase approximation (RPA). The Bi₂Te₂Se, Bi₂Te₃ and Bi₂Te₂Se/Bi₂Te₃ heterostructure shown a broad absorption spectrum and maximum value of absorption coefficient are 3.07, 2.9 and 3.06 eV, respectively. In order to meet the future demand for innovative optoelectronic applications, this study offers a fundamental understanding of the impulsive interfacial stimulation of TI-based heterojunction and experimentally synthesized photodetector with exceptional efficiency.
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