This paper presents the development of a regrowth method and ionic doping modification to achieve photodetection in the very long wave infrared (VLWIR) region using colloidal quantum dots (CQDs). The researchers demonstrate a photodetector based on HgTe CQDs that can detect light up to 18 μm wavelength. At liquid nitrogen temperature, the responsivity reaches 0.3 A/W and 0.13 A/W for 18 μm and 10 μm CQD photoconductors, respectively, with specific detectivity of 6.6 × 10^8 Jones and 2.3 × 10^9 Jones. The work addresses the challenge of extending the photodetection wavelength of CQDs beyond the mid-wave infrared (MWIR) region, which is currently limited by the small size and poor colloidal stability of CQDs. The regrowth method and ionic doping modification improve carrier mobility by a factor of 100, enhancing carrier transport efficiency. The results show that the responsivity is limited by the ratio between the carrier drift length and the electrode gap, as well as the absorption coefficient. This study expands the photodetection wavelength range of CQDs and highlights the potential of bottom-up infrared photodetection with lower costs compared to epitaxial growth semiconductor bulk.This paper presents the development of a regrowth method and ionic doping modification to achieve photodetection in the very long wave infrared (VLWIR) region using colloidal quantum dots (CQDs). The researchers demonstrate a photodetector based on HgTe CQDs that can detect light up to 18 μm wavelength. At liquid nitrogen temperature, the responsivity reaches 0.3 A/W and 0.13 A/W for 18 μm and 10 μm CQD photoconductors, respectively, with specific detectivity of 6.6 × 10^8 Jones and 2.3 × 10^9 Jones. The work addresses the challenge of extending the photodetection wavelength of CQDs beyond the mid-wave infrared (MWIR) region, which is currently limited by the small size and poor colloidal stability of CQDs. The regrowth method and ionic doping modification improve carrier mobility by a factor of 100, enhancing carrier transport efficiency. The results show that the responsivity is limited by the ratio between the carrier drift length and the electrode gap, as well as the absorption coefficient. This study expands the photodetection wavelength range of CQDs and highlights the potential of bottom-up infrared photodetection with lower costs compared to epitaxial growth semiconductor bulk.