scholarly journals A flexible capacitive photoreceptor for the biomimetic retina

2022 ◽  
Vol 11 (1) ◽  
Author(s):  
Mani Teja Vijjapu ◽  
Mohammed E. Fouda ◽  
Agamyrat Agambayev ◽  
Chun Hong Kang ◽  
Chun-Ho Lin ◽  
...  

AbstractNeuromorphic vision sensors have been extremely beneficial in developing energy-efficient intelligent systems for robotics and privacy-preserving security applications. There is a dire need for devices to mimic the retina’s photoreceptors that encode the light illumination into a sequence of spikes to develop such sensors. Herein, we develop a hybrid perovskite-based flexible photoreceptor whose capacitance changes proportionally to the light intensity mimicking the retina’s rod cells, paving the way for developing an efficient artificial retina network. The proposed device constitutes a hybrid nanocomposite of perovskites (methyl-ammonium lead bromide) and the ferroelectric terpolymer (polyvinylidene fluoride trifluoroethylene-chlorofluoroethylene). A metal-insulator-metal type capacitor with the prepared composite exhibits the unique and photosensitive capacitive behavior at various light intensities in the visible light spectrum. The proposed photoreceptor mimics the spectral sensitivity curve of human photopic vision. The hybrid nanocomposite is stable in ambient air for 129 weeks, with no observable degradation of the composite due to the encapsulation of hybrid perovskites in the hydrophobic polymer. The functionality of the proposed photoreceptor to recognize handwritten digits (MNIST) dataset using an unsupervised trained spiking neural network with 72.05% recognition accuracy is demonstrated. This demonstration proves the potential of the proposed sensor for neuromorphic vision applications.

Polymers ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2344
Author(s):  
Deepalekshmi Ponnamma ◽  
Mariem Mohammed Chamakh ◽  
Abdulrhman Mohmmed Alahzm ◽  
Nisa Salim ◽  
Nishar Hameed ◽  
...  

Flexible piezoelectric nanogenerators (PENG) are widely applied to harvest sustainable energy from multiple energy sources. The rational and simple design of PENG have great potential in soft electronics. Here we design a highly flexible PENG using the polyvinylidene fluoride (PVDF) and its copolymer, polyvinylidene hexafluoropropylene (PVDF-HFP) with two nanoarchitectures of semiconducting metal oxides, TiO2 and ZnO. The nanotubes of TiO2 and nanoflowers of ZnO are embedded in these different polymeric media by solvent mixing, and new fiber mats are generated by coaxial electrospinning technique. This process aligns the dipoles of polymers and nanomaterials, which is normally a pre-requisite for higher piezo potential. With excellent mechanical strength and flexibility, the tailored lightweight fiber mats are capable of producing good output voltage (a maximum of 14 V) during different mechanical vibrations at various frequencies and in response to human motions. The hybrid nanocomposite PENG is durable and inexpensive and has possible applications in wearable electronics.


2019 ◽  
Vol 14 (8) ◽  
pp. 776-782 ◽  
Author(s):  
Feichi Zhou ◽  
Zheng Zhou ◽  
Jiewei Chen ◽  
Tsz Hin Choy ◽  
Jingli Wang ◽  
...  

2013 ◽  
Vol 4 ◽  
pp. 611-624 ◽  
Author(s):  
Renate Hiesgen ◽  
Seniz Sörgel ◽  
Rémi Costa ◽  
Linus Carlé ◽  
Ines Galm ◽  
...  

In this work, material-sensitive atomic force microscopy (AFM) techniques were used to analyse the cathodes of lithium–sulfur batteries. A comparison of their nanoscale electrical, electrochemical, and morphological properties was performed with samples prepared by either suspension-spraying or doctor-blade coating with different binders. Morphological studies of the cathodes before and after the electrochemical tests were performed by using AFM and scanning electron microscopy (SEM). The cathodes that contained polyvinylidene fluoride (PVDF) and were prepared by spray-coating exhibited a superior stability of the morphology and the electric network associated with the capacity and cycling stability of these batteries. A reduction of the conductive area determined by conductive AFM was found to correlate to the battery capacity loss for all cathodes. X-ray diffraction (XRD) measurements of Li2S exposed to ambient air showed that insulating Li2S hydrolyses to insulating LiOH. This validates the significance of electrical ex-situ AFM analysis after cycling. Conductive tapping mode AFM indicated the existence of large carbon-coated sulfur particles. Based on the analytical findings, the first results of an optimized cathode showed a much improved discharge capacity of 800 mA·g(sulfur)−1 after 43 cycles.


2021 ◽  
Author(s):  
Yu-Chi Chang ◽  
Jia-Cheng Jian ◽  
Ya-lan Hsu ◽  
Sheng-Po Chang ◽  
Shoou-Jinn Chang

Abstract A photonic memristor is a component used in photonic and neuromorphic computing that can complete the high-speed programming of nonvolatile data through light illumination`. To date, photonic memristors have been fabricated using several methods. Applied principles include the photovoltaic (PV) effect-mediated Schottky barrier, PV effect-induced formation/annihilation of conductive filaments, photogating effect and photoinduced chemical reaction/conformation change5. However, currently proposed solutions are half sets only (i.e. either light writing or light erasing only), photoinduced electrical programming or photovoltaically modulated6-9. Moreover, these devices frequently require the use of special materials or complex device structures and circuitries5. Here, we used a mixture of apple pectin (AP) and nickel oxide (NiO) nanoparticles (NPs) as the resistive switching layer and fabricated a simple metal/insulator/metal sandwich structure. The surface defects between the interface of AP and NiO NPs can capture ultraviolet-excited electrons and convert the resistance state into low-resistance state (LRS). By expelling the electrons in the traps through green light, LRS can be transformed back into high-resistance state. The memory can be programmed purely through light and is compatible with electrical operation. This discovery provides a reliable method for fabricating photonic memristors that can be adopted in photonic and neuromorphic computing applications.


Nanomaterials ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 915 ◽  
Author(s):  
Lei Shi ◽  
Huiying Hao ◽  
Jingjing Dong ◽  
Tingting Zhong ◽  
Chen Zhang ◽  
...  

Intermediate phase is considered an important aspect to deeply understand the crystallization procedure in the growth of high-quality perovskite layers by an anti-solvent technique. However, the moisture influence on the intermediate phase formation is not clear in air conditions as yet. In this work, pure (FA0.2MA1.8)Pb3X8(DMSO·DMF) intermediate phase was obtained in as-prepared perovskite film by spin-coating the precursor of co-solvent (DMSO and DMF) in an ambient air (RH20–30%). Moreover, the appropriate quantity of ethyl acetate (C4H8O2, EA) also controls the formation of pure intermediate phase. The uniform and homogeneous perovskite film was obtained after annealing this intermediate film. Therefore, the best power conversion efficiency (PCE) of perovskite solar cells (PSCs) is 16.24% with an average PCE of 15.53%, of which almost 86% of its initial PCE was preserved after 30 days in air conditions. Besides, the steady-state output efficiency ups to 15.38% under continuous illumination. In addition, the PCE of large area device (100 mm2) reaches 11.11% with a little hysteresis effect. This work would give an orientation for PSCs production at the commercial level, which could lower the cost of fabricating the high efficiency PSCs.


2021 ◽  
Vol 42 (1) ◽  
pp. 013105
Author(s):  
Fuyou Liao ◽  
Feichi Zhou ◽  
Yang Chai

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