Occupying discrete electronic states of a conduction band with electrons by tuning non-stoichiometry, a phenomenon known as self-doping, provides a powerful platform for exploring higher quantized states of a colloidal quantum dot(CQD). Here, we report three tunable intraband transitions in mid-wavelength infrared to long-wavelength infrared and very-long-wavelength infrared (λ > 15 µm) arising from broken-degeneracy in the conduction band of quantum dots. We demonstrated the three electronic transitions by using FT-infrared absorption, FT-infrared photoluminescence, and FT-infrared photocurrent spectroscopy. In analogy with the atomic p-orbital, the quantum dot exhibits a p-like confined energy level in the conduction band arising from spatial quantization. Interestingly, the electronic transitions with the same angular momentum quantum number between 1Pe states, below 25 meV, are successfully detected by terahertz spectroscopy, suggesting that the 1Pe states of CQDs are not strictly orthogonal.
https://doi.org/10.1002/lpor.71333Digital Object Identifier (DOI)