Scientists in China and Singapore have collaborated to introduce a self-powered photodetector that can be emoloyed in an extensive range of applications like chemical analysis and more. Typically, photodetectors need an external voltage to offer the driving force for separating and estimating photo-generated electrons that comprise the identification.
To eradicate this need, the scientific group led by Junling Wang and Le Wang at Nanyang Technological University in Singapore introduced a new, stable and sensitive photodetector based on a semiconducting junction known as GdNiO3/Nb-dopes SrTiO3 p-n heterojunction. An inherent electrical field at the GNO/NSTO interface offers the driving force for effective separation of photo-generated carriers, eradicating the requirement for an external power source.
In addition to its self-powered feature, Wang and his group reports tuning the substance properties to achieve broad sensitivity. For such compounds, most research work thus far has emphasized on studying the origin of metal-insulator transition, but this group took a distinct approach.
The properties of perovskite nickelates, the category of solar cell substances in which such structure fails, are highly sensitive to oxygen content. Such sensitivity allows fine tuning of the final electronic structures by varying the oxygen environment during film deposition..
“Our work is new and confirms that nickelates films have tunable band gaps with altering of the oxygen vacancy concentration that makes them suitable as light absorbing substances in optoelectronic devices,” says Wang. “Employing the self-powered photodetector we designed, we study its photo responsivity using light sources with distinct wavelengths, with major photo-response appearing when the light wavelength diminishes to 650 nanometers,” says Wang.
A major challenge in developing such photodetector was determining the accurate band structure or energy structure available to electrons of the 10 nanometer thick GNO films. “To avail the band structure, we used both spectroscopic ellipsometry measurements and ultraviolet photoelectron spectroscopy (UPS) measurements,” says Wang. Using the deduced values for the optical bandgap from such estimations, along with known limits and values for GNO layers, they could plot the energy levels and work functions of the numerous components in the devices.
The group expects to explore more substances with similar features. “One of the finest features of nickelates is the dependence of their physical properties on the selected rare earth element,” says Wang. “So far, we have only examined GdNiO3 layer, but besides that we can also identify other “R”-NiO3 films where “R” can be Sm, Nd, Lu, and Er and study their potential applications in the photodetector.”
The group also intends to enhance the performance of the photodetector by adding an insulating SrTiO3 layer sandwiched between the NSTo substrate and GdNiO3 film.
Such new study has excellent potential for applications employing optoelectronic devices. “We believe that such paper will augment further studies and enlarge the potential applications of systems based on nickelates,” says Wang
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