Compared with other properties such as electrical conductivity and field emission, CuO nanostructures' optical properties have been much less investigated and discussed. As a p-type semiconductor, a narrow bandgap of around 1.2 eV was reported for bulk CuO. Reported bandgap values for CuO needed to be in better agreement; for example, a bandgap in the range of 1.56 and 1.85 eV was reported for CuO thin films. In addition, the variation of bandgap could also relate to the quantum size effect in different CuO nanostructures. In literature, absorption techniques have mainly assessed the optical behavior of CuO nanomaterials.
In contrast, luminescence techniques, which are essential tools for investigating electronic transitions in semiconductors—including band edge or near band edge transitions—have seldom been used. The low emission efficiency of CuO is the main reason for the lack of luminescence data for CuO nanomaterials; also, the results on the origin of the luminescence of CuO remain contradictory. There are several photoluminescence bands generally reported for CuO nanostructures that expand from UV to near IR region; however, the most frequent peaks fall in the region from 400 to 600 nm. Generally, the deep-level emission in CuO consists of a green emission at around 605 nm and a near-yellow emission at about 680 nm. Though the origin of deep-level emission in CuO is under debate, and little information is available on the CuO defect structure, the deep emissions are generally supposed to relate to defects in CuO nanomaterial. CuO is intrinsically a p-type semiconductor due to the existence of Cu vacancies. If you are looking for high quality, high purity, and cost-effective copper oxide, or if you require the latest price, please email contact mis-asia.
