Infrared materials recently attract much interest because of the demand for novel infrared applications and research aspects. Among the infrared materials, the self-doped colloidal quantum dots (CQDs) have shown the unique mid wavelength infrared (MWIR) transition. This unique MWIR transition originated at the higher quantum state, namely intraband transition. The small energy gap is a great candidate for applications such as sensors, LEDs, detectors, etc. This poster will present the recent discovery of the physical properties and applications for the MWIR self-doped CQDs.

             The self-doped CQDs have intrinsic n-type properties that show electron occupation in the other quantum states than band-to-band transition. The self-doping property can be controlled with the synthetic procedure to fill the electron(s) to a particular state. The HgSe CQDs have revealed that the singly and doubly occupied quantum states (SOQS and DOQS) are achievable by changing the reaction time. The SOQS and DOQS are possible because of intrinsic self-doping n-type doping property, which simultaneously increases the Fermi level of materials. Therefore, the HgSe CQDs' intrinsic n-type doping character is carried to develop a multi-sensible TFT device that can detect gas molecules, biomolecules, or MWIR photons. Due to the Fermi level increment, the CdHgSe alloy could successfully demonstrate a physical phase change from semiconductor to the metal. The optical property of the alloy reflects the physical class change is correlated to the gradual redshift towards the infrared region, which arose by the self-doping. Surprisingly, FTIR data show an enhanced localized surface plasmon resonance (LSPR) intensity with respect to the mercury cation ratio enriched in the alloy. Thus, it is safe to argue that the self-doping character induces the carrier concentration augmentation in the material. The silver selenide (Ag2Se) CQDs is a less toxic material found to have an intraband transition in the MWIR region. Strikingly, it is observed that the crystal phase transition establishes the 1P_e state peak splitting of the Ag₂Se CQDs. Furthermore, the Ag₂Se CQDs show the coexistence of LSPR and intraband transition revealing the quantum-plasmon characteristics in a single crystal. Therefore, the self-doped CQDs show great potential to provide novel research and applications such as optoelectronics, biomedical, quantum computing, renewable energy, etc.