Enhanced carrier separation assisted high-performance piezo-phototronic self-powered photodetector based on core-shell ZnSnO3 @In2O3 heterojunction

Enhanced carrier separation and inbuilt electric field are recommended to demonstrate self-powered, high-performance photodetectors. Traditionally, planar, bulk, and vertical heterojunctions are used for fabrication of photodetectors.In this work, we demonstrate a self-powered piezo-phototronic photodetector using a unique coaxial n-n heterojunction i.e., ZnSnO3/In2O3 core-shell nanofibers synthesized using electrospinning. The detailed morphological characterization reveals the formation of ZnSnO3 core and In2O3 shell nanofiber while structural studies confirm the non-centrosymmetric cubic In2O3, with a space group of I213 and rhombohedral ZnSnO3 with R3c space group. The Piezo force microscopy (PFM studies displayed a piezoelectric coefficient (d33) value of the ZnSnO3/In2O3 nanofibers was obtained as 254 pm/V. The fabricated piezo-phototronic device displays a superior photo-response upon illumination of UV light at zero bias owing to the built-in electric potential. The optimized UV photodetector displayed a large Ion/Ioff ratio of 102. Upon application of a compressive strain of 4.3%, the device exhibits an increase in photocurrent up to 58% and upon the tensile strain of 3.2%, the device shows a decrease in photocurrent up to 24%. The obtained results can be attributed to the enhanced carrier separation in the coaxial interfaces of ZnSnO3/In2O3 junctions, thus improving the ability to detect UV light. The fabricated device exhibits a maximum responsivity and detectivity of 0.7 mA/W and 8.3 × 109 Jones respectively which are far superior to the existing class of similar devices fabricated using sophisticated cleanroom techniques Further, a stable photo-response even after 1000 bending cycles proves its mechanical robustness. This work provides a promising strategy for improving the responsivity and detectivity of photodetectors as well as a unique coaxial nanostructure for self-powered, UV light detection for optoelectronic applications. © 2022 Elsevier Lt

Low-density, stretchable, adhesive PVDF-polypyrrole reinforced gelatin based organohydrogel for UV photodetection, tactile and strain sensing applications

In this work, we report an adhesive, mechanically robust Polyvinylidene fluoride (PVDF)-polypyrrole reinforced gelatin organohydrogel as a multifunctional, and conductive platform for photodetector, highly sensitive tactile, and strain sensor applications. Morphological studies reveal the formation of PVDF/polypyrrole/gelatin microspheres enclosed with nanosheets like structure on the surface of the organohydrogel confirming the interaction of the primary amines of the cationic PVDF-polypyrrole nanocomposite with the anionic carboxylic chains of gelatin. Structural characterization confirms the characteristic scattering bands of β- phased PVDF and polypyrrole. The synthesized organohydrogel when used as a UV photodetector exhibits a rapid response time of 25 ms, excellent responsivity of 14 A/W and external quantum efficiency of 26%, caused due to the effective separation of photogenerated charge carriers at the polymer-hydrogel interface. The recoverable organohydrogel-based tactile sensor exhibited a sensitivity of 32.39 kPa−1 in the wide linear range of 0.1 – 55 kPa. Further, the strain sensor displayed a gage factor of 27.8 in the dynamic sensing range of 8.6% to 61% which is much higher than the existing class of similar reports. The sensing mechanism can be attributed to the piezo-electric polarizability of the β- phase PVDF and high conductivity of polypyrrole and gelatin in the flexible organohydrogel. The effective reinforcement of PVDF and polypyrrole in the gelatin matrix enhances the tensile strength, elastic properties, conductivity with least dependency on humidity and temperature. The polymer composite reinforced gelatin organohydrogel has a shelf-life of 30 days. © 202

Lead-free PDMS/PPy based low-cost wearable piezoelectric nanogenerator for self-powered pulse pressure sensor application

Self-powered biocompatible electronic devices to detect vital physiological signals of the human body are in great demand in wearable applications. In this work, a low-cost polydimethylsiloxane/polypyrrole composite polymer film-based piezoelectric nanogenerator is fabricated and utilized as a self-powered arterial pulse pressure sensor. XRD and Raman analysis are used to confirm the crystal structural orientation and chemical composition of composite polymer, respectively. Uniform and crack-free morphology of PDMS/PPy composite polymer film is confirmed via Field Emission Scanning Electron Microscopy, while Energy Dispersive X-Ray is used to study the elemental analysis of composite polymer film, which confirms that there is no extra impurity present in the system. A flexible and robust piezoelectric nanogenerator with device configuration of Al coated PET/(PDMS: PPy)/ ITO coated PET is fabricated that gives an output voltage of 12 V and current density of 0.11 µA/cm2 when 1.47 N/cm2 pressure is applied. The biocompatible nanogenerator as a self-powered pulse sensor is demonstrated, thus proving its potential for developing versatile self-powered systems useful in biomedical applications. © 202

NiO nanofibers interspersed sponge based low cost, multifunctional platform for broadband UV protection, ultrasensitive strain and robust finger-tip skin inspired pressure sensor

We report for the first time a low cost, tactile, high performance, multifunctional sensing platform for applications namely broadband Ultraviolet (UV) filter, strain sensor and finger-tip based pressure sensor. Eco-friendly, light weight and mechanically stable melamine sponge (MS) was chemically engineered using electrospun NiO nanofibers for facile fabrication of the tactile sensor. Detailed characterization studies revealed NiO nanofibers interspersed within the structure of hexagonal voids present in melamine sponge. Under optimal conditions, the UV filter exhibited a remarkable UPF (UV Protection Factor) of 87.7, the strain sensor exhibited a gauge factor of 34 with a maximum strain withstanding capability of 76.3% and the pressure sensor displayed a wide dynamic sensing range of 50 N–700 N with a sensitivity 3.75 kPa−1 which are significantly higher than similar sensors fabricated using advanced methodologies. Furthermore, the device was found to be highly robust and displayed excellent stability up to 500 cycles of bending. The mechanism of the multifunctional sensor can be attributed to the controllable deformation of NiO nanofibers distributed across the melamine sponge upon external strain and pressure. The sensor was successfully demonstrated as strain sensor and pressure sensor for wearable motion detection and ultra-sensitive virtual keyboard applications respectively. The strategy employed here paves way towards integrating multiple devices to develop versatile, clean room-free, low-cost, multifunctional sensors useful in consumer electronics and healthcare

1D NiO-3D Fe2O3mixed dimensional heterostructure for fast response flexible broadband photodetector

Conventional heterojunction photodetectors rely on planar junction architecture which suffer from low interfacial contact area, inferior light absorption characteristics and complex fabrication schemes. Heterojunctions based on mixed dimensional nanostructures such as 0D-1D, 1D-2D, 1D-3D etc have recently garnered exceptional research interest owing to their atomically sharp interfaces, tunable junction properties such as enhanced light absorption cross-section. In this work, a flexible broadband UV-vis photodetector employing mixed dimensional heterostructure of 1D NiO nanofibers and 3D Fe2O3 nanoparticles is fabricated. NiO nanofibers were synthesized via economical and scalable electro-spinning technique and made composite with Fe2O3 nanoclusters for hetero-structure fabrication. The optical absorption spectra of NiO nanofibers and Fe2O3 nanoparticles exhibit peak absorption in UV and visible spectra, respectively. The as-fabricated photodetector displays quick response times of 0.09 s and 0.18 s and responsivities of 5.7 mA W-1 (0.03 mW cm-2) and 5.2 mA W-1 (0.01 mW cm-2) for UV and visible spectra, respectively. The fabricated NiO-Fe2O3 device also exhibits excellent detectivity in the order of 1012 jones. The superior performance of the device is ascribed to the type-II heterojunction between NiO-Fe2O3 nanostructures, which results in the localized built-in potential at their interface, that aids in the effective carrier separation and transportation. Further, the flexible photodetector displays excellent robustness when bent over ∼1000 cycles thereby proving its potential towards developing reliable, diverse functional opto-electronic devices. © 2022 IOP Publishing Ltd