Highly spectrum-selective ultraviolet photodetector based on p-NiO/n-IGZO thin film heterojunction structure

The dual-detection mode and improved photoresponse of IGZO-based photodetectors by interfacing with water-soluble biomaterials

The use of conventional fabrication methods rapidly developed the performance and notable enhancements of optoelectronic devices. However, it proved challenging to develop and demonstrate stable optoelectronic devices with biodegradability and biocompatibility properties towards sustainable development and extensive applications. This study incorporates a water-soluble Cr-phycoerythrin (Cr-PE) biomaterial to observe its optical and electronic properties effects on the pristine indium gallium zinc oxide (IGZO)-based photodetector. The fabricated photodetector demonstrates an extended absorption detection region, enhanced optoelectronic performance, and switchable function properties. The resulting photocurrent and responsivity of the IGZO/Cr-PE structure have increased by 5.7 and 7.1 times as compared to the pristine IGZO photodetector. It was also observed that the photodetector could operate in UV and UV-visible with enhanced optical properties by effectively adding the water-soluble Cr-PE. Also, the sensing region of IGZO photodetector becomes changeable. It exhibits switchable dual detection by alternatively dripping and removing the Cr-PE on the IGZO layer. Different measurement parameters such as detectivity, repeatability, and sensitivity are highlighted to effectively prove the advantage of including Cr-PE on the photodetector structure. This study contributes to understanding the potential functions in improving optoelectronic devices through an environmental-friendly method.

Plasmonic Ag nanoparticles arbitrated enhanced photodetection in p-NiO/n-rGO heterojunction for future self-powered UV photodetectors

We report on the low cost and low temperature chemical synthesis of p-type nickel oxide (NiO) and n-type reduced graphene oxide (rGO) and their integration onto ITO/glass substrate to form p-NiO/n-rGO heterojunction for possible self-powered ultraviolet (UV) photodetector applications. Different spectroscopies and microscopes were employed to study their microstructural and surface properties. Whereas, the electrical characterizations have been performed on the devices to ascertain the responsivity, detectivity, external quantum efficiency and temporal responses under dark and UV illumination. It is noteworthy that rGO has not only been used as an n-type semiconductor, but also acted as an electron transport layer, which satisfactorily separates out the electrons from the generated carrier pairs, leading to enhanced photoresponse. Furthermore, efforts were also consecrated to synthesize Ag nanoparticles (NPs) of ∼5 nm radius. The integration of Ag NPs on the conventional NiO/rGO heterojunction facilitates an improved UV light absorption property. It was understood that the performance improvement was owed to the local surface plasmon resonance of Ag NPs within the active layer of NiO. Surprisingly, both the devices (with and without Ag NPs) exhibit photovoltaic behavior which shows its potential for self-powered device application. When the Ag NPs embedded device is concerned, it showed better on/off ratio (6.3 × 10³), high responsivity (72 mAW^-1), large detectivity (3.95 × 10¹² Jones), and high efficiency (24.46%) as compared to the conventional NiO/rGO heterojunction one (without Ag NPs). The variation in the photoresponse and improved charge transport was explained through a band-diagram, which also showcases a comprehensive understanding on the operational principle of the fabricated self-powered devices. Thus, this self-powered photodetector driven by built in electric field is operated independently and can be attached with any other electronic gadgets for internet of things applications.

Controlling Carrier Type and Concentration in NiO Films To Enable in Situ PN Homojunctions

The oxygen partial pressure during NiO deposition in reactive sputtering of a Ni target is used to control its carrier type and concentration, obtaining both n- and p-type films. Carrier concentration can be controlled, ranging from 10¹⁹ to 10¹⁴ cm^-3. Films deposition is performed at 200 °C, a relatively low temperature that enables the use of glass as substrate. Experimental band diagrams for n-type NiO are obtained for the first time. Finally, a NiO homojunction is demonstrated by introducing a low carrier concentration layer in between n- and p⁺-type NiO layers. Layers are deposited in situ, preventing contamination and improving the interface quality, as observed by TEM. The Ni:O ratio for each layer was also obtained by analytical TEM measurements, demonstrating the impact of the oxygen partial pressure on the films' stoichiometry and the simplicity of our process to control carrier type and carrier concentration in oxide semiconductors.

Large area transparent ZnO photodetectors with Au wire network electrodes

A large area highly transparent UV photodetector is fabricated using Au wire networks as transparent electrodes and ZnO as the active layer.

High spectrum selectivity and enhanced responsivity of a ZnO ultraviolet photodetector realized by the addition of ZnO nanoparticles layer

A photodetector with a high spectrum selectivity and enhanced responsivity has been realized in the ZnO NPs coated Au/ZnO/Au structure.