Energy band engineering is a promising method to tune the photoelectric properties of semiconductors. In this paper, we report an un-element-doped ZnO nanorod array film with a degenerate energy band via annealing in a hydrogen atmosphere. Due to the energy band modification, the photogenerated carrier transitions in the degenerate energy band, involving the valance band, the defect bands and the degenerate conduction band, cause unique photoelectric properties in the degenerate ZnO film. The degenerate ZnO film performs with outstanding conductivity and exhibits an obvious optical absorption in the visible region. Its photoluminescence and photoresponse properties are investigated to understand the fundamentals of photogenerated carrier excitation and recombination in the degenerate ZnO film. Interestingly, the degenerate ZnO film performs with poor photoresponse and has poor photocurrent efficiencies for ultraviolet, blue, and green illuminations, but the photoresponse for near-infrared illumination is attractive. Our results also demonstrate the selectively enhanced down-conversion photoluminescence both at the UV band and at the near-infrared band from the degenerate ZnO film after being excited by an ultraviolet laser source.

Narrow bandgap semiconductor‐based photodetectors often suffer from high room‐temperature noise and are therefore operated at low temperatures. Here, a hybrid poly(3‐hexylthiophene) (P3HT): HgTe quantum dot (QD) phototransistor is reported, which exhibits high sensitivity and fast photodetection up to 2400 nm wavelength range at room temperature. The active layer of the phototransistor consists of HgTe QDs well dispersed in a P3HT matrix. Fourier‐transform infrared spectra confirm that chemical grafting between P3HT and HgTe QDs is realized after undergoing prolonged coblend stirring and a ligand exchange process. Thanks to the shifting of the charge transport into the P3HT and the partial passivation of the surface traps of HgTe QDs in the blend, the P3HT: HgTe QD hybrid phototransistor shows significantly improved gate‐voltage tuning, 15 times faster response, and ≈80% reduction in the noise level compared to a pristine HgTe QD control device. More than 10¹¹ Jones specific detectivity (estimated from the noise spectral density measured at 1 kHz) is achieved at room temperature, and the response time (measured at 22 mW cm⁻² illumination intensity) of the device is less than 1.5 µs. That is comparable to commercial epitaxially grown IR photodetectors operated in the same wavelength range.

The inverse room-temperature gas-sensing behavior of NiO and rGO–NiO in different ranges of NO₂ concentration.