SEMINAR LMGP - 23.03.2021 - Guislain HECTOR

Guislain HECTOR
Ph.D. student,
LMGP

Detecting the ultra-violet (UV) and solar radiation is of primary importance for a wide variety of applications, including UV photodetectors and solar cells. A large part of these devices is based on the use of two-dimensional thin films made of direct band gap semiconductors with a relevant band gap energy. However, their cost, materials/energy consumption, as well as their performances make them incompatible with their use in nanoscale devices. In order to comply with these challenges, new architectures based on ZnO core-shell nanowire (NW) heterostructures have received an increasing interest. In these architectures, ZnO NWs play the role of an electron transporting materials and their physical properties directly affect the performances of the devices. Here, ZnO NW arrays are grown by the low cost and easily scalable chemical bath deposition (CBD) technique. The effect of adding indium nitrate in solution on the morphology and properties of ZnO NWs grown by CBD is investigated in detail. Different pH and concentrations of indium dopant in solution are studied. The results are discussed in the light of chemical reactivity and thermodynamic computations. As an example of ZnO core-shell NW heterostructures, an extremely-thin absorber (ETA) solar cell using a double TiO₂/Sb₂S₃ shell is developed. The thickness of the Sb₂S₃ shell is varied on a broad range and the related optical and electrical properties are reported. They display promising photovoltaic performances in the field of ETA solar cells. As a promising wide band gap (WBG) semiconductor for UV photodetectors, the CBD of gallium oxide (Ga₂O₃) on silicon is also explored. The influence of the concentration of gallium nitrate on the morphology of Ga₂O₃ microrods is highlighted. These works provide interesting perspectives for the development of ZnO NW-based heterostructures for low cost and nanoscaled devices in the field of optoelectronics and energy.