Two-dimensional (2D) transition metal carbides (MXenes) show promising properties in a vast range of applications due to their unique properties, including 2D layered structure, large physical surface area, high electronic conductivity, and tailorable surface properties. The layered structure with weak physical forces between the layers poses a significant challenge due to the restacking tendency, resulting in a substantial decrease in the surface area. The electronic properties of 2D materials can be tuned by introducing heteroatoms into the layers. Herein, we designed novel electronic materials with a three-dimensional structure via a facile post-treatment of 2D V<inf>2</inf>CT<inf>x</inf> MXene layers. Then, nitrogen (N) and sulfur (S) atoms were used to tune the electronic properties of 3D V<inf>2</inf>CT<inf>x</inf> MXenes. The electronic properties of heteroatom-doped 3D MXenes were exploited as interlayer materials between a silicon wafer and aluminum to develop Schottky-type self-powered UV–Vis–NIR photodetector devices. Our results indicated that the MXene nanocomposite had excellent semiconductor behavior, confirming its potential for optoelectronic applications. Electrical parameters such as ideality factor and barrier height were efficiently estimated using various machine learning models, including linear regression and artificial neural networks. The MXene/n-Si device demonstrated superior performance under zero-bias operation, achieving a peak photocurrent of 3.78×10⁻⁶ A, responsivity of 13.18 mA/W, and detectivity up to 6.53×10¹⁰ Jones in the visible region (600 nm). In the UV range (351 nm), the device maintained reliable detection with photocurrents up to 5.97×10⁻⁷ A, responsivity of 3.80 mA/W, and detectivity of 1.88×10¹⁰ Jones. Even in the NIR region (1000 nm), it sustained strong performance with detectivity above 5.55×10¹⁰ Jones. These results highlight the MXene/n-Si heterojunction’s potential for high-sensitivity, broadband, and energy-efficient photodetection across the UV–VIS–NIR spectrum.