The escalating demand for cost-effective, flexible, and solution-processed materials in infrared (IR) photodetection presents a compelling alternative to current epitaxially grown optoelectronic technology. Colloidal quantum dots (CQDs) have emerged as a versatile platform for optoelectronic device fabrication, offering affordability, low-temperature synthesis, and scalability. Specifically, mercury chalcogenide CQDs exhibit notable intraband absorption in the mid-IR region. In this study, we explore an intraband HgSe-HgTe CQD photodetector structure tailored for mid-IR light detection. Through numerical optimization, we engineer detectivity by varying key design parameters—the film doping density, CQD diameter, and number of periods in the active layer—under different temperatures and biases. Results indicate that, at 60 K and 1 V bias, our optimally designed HgSe-HgTe CQD IR photodetector attains a peak detectivity of 8.14×1010 Jones for a film doping density of 1019 cm−3 of HgSe CQDs, 9.34×1010 Jones for HgSe CQDs with a 4.8 nm diameter, and 8.72×1010 Jones for 9 periods of HgSe-HgTe CQDs.