A joint team of reserachers from Singapore and China have developed a self-powered photodetector that can be used in a wide range of applications such as chemical analysis, communications, astronomical investigations and much more.
Typically, photodetectors require an external voltage to provide the driving force for separating and measuring photo-generated electrons that comprise the detection. To eliminate this need, the research team led by Junling Wang and Le Wang at Nanyang Technological University in Singapore developed a novel, sensitive and stable photodetector based on a semiconducting junction called a GdNiO3/Nb-doped SrTiO3 (GNO/NSTO) p-n heterojunction. An inherent electric field at the GNO/NSTO interface provides the driving force for efficient separation of photo-generated carriers, eliminating the need for an external power source.
In addition to its self-powered feature, Wang and his team reported tuning the material properties to achieve broad sensitivity. For these compounds, most research work thus far has focused on studying the origin of metal-insulator transition, but this team took a different approach.
The properties of perovskite nickelates, the category of solar cell materials in which this structure falls, are very sensitive to oxygen content. This sensitivity enables fine tuning of the final electronic structures by varying the oxygen environment during film deposition (constructing the heterojunction).
A significant challenge in developing this photodetector was determining the correct band structure, or energy structure available to electrons, of the 10 nanometer thick GNO films. To obtain the band structures, they used both spectroscopic ellipsometry measurements and ultraviolet photoelectron spectroscopy (UPS) measurements. Using the deduced values for the optical bandgap from these measurements, along with known limits and values for GNO films, they could plot the energy levels and work functions of the various components in the devices.
The team hopes to explore more materials with similar features. The team also plans to improve the performance of the photodetector by adding an insulating SrTiO3 (STO) layer sandwiched between the GdNiO3 film and NSTO substrate. This novel work has great potential for applications using optoelectronic devices. Click here to read the published paper.
