Showing papers by "Ying Fang published in 2017"

Highly Narrowband Photomultiplication Type Organic Photodetectors.

Abstract: Filterless narrowband response organic photodetectors (OPDs) present a great challenge due to the broad absorption range of organic semiconducting materials. The reported narrowband response OPDs also suffer from low external quantum efficiency (EQE) in the desired response window and low rejection ratio. Here, we report highly narrowband photomultiplication (PM) type OPDs based on P3HT:PC71BM (100:1, wt/wt) as active layer without an optical filter. The full width at half-maximum (fwhm) of the PM-type OPDs can be well retained less than 30 nm under different biases. Meanwhile, the champion EQE and rejection ratio approach 53 500% and 2020 at −60 V bias, respectively. The small fwhm should be attributed to the sharp absorption edge of active layer with small amount of PC71BM. The PM phenomenon is attributed to hole tunneling injection from the external circuit assisted by trapped electron in PC71BM near the Al electrode under light illumination. These highly narrowband PM-type OPDs should have great poten...

Highly Sensitive Low-Bandgap Perovskite Photodetectors with Response from Ultraviolet to the Near-Infrared Region

Abstract: It is a great challenge to obtain broadband response perovskite photodetectors (PPDs) due to the relatively large bandgaps of the most used methylammonium lead halide perovskites. The response range of the reported PPDs is limited in the ultraviolet–visible range. Here, highly sensitive PPDs are successfully fabricated with low bandgap (≈1.25 eV) (FASnI3)0.6(MAPbI3)0.4 perovskite as active layers, exhibiting a broadband response from 300 to 1000 nm. The performance of the PPDs can be optimized by adjusting the thicknesses of the perovskite and C60 layers. The optimized PPDs with 1000 nm thick perovskite layer and 70 nm thick C60 layer exhibit an almost flat external quantum efficiency (EQE) spectrum from 350 to 900 nm with EQE larger than 65% under −0.2 V bias. Meanwhile, the optimized PPDs also exhibit suppressed dark current of 3.9 nA, high responsivity (R) of over 0.4 A W−1, high specific detectivity (D*) of over 1012 Jones in the near-infrared region under −0.2 V. Such highly sensitive broadband response PPDs, which can work well as self-powered conditions, offer great potential applications in multicolor light detection.

Photomultiplication type narrowband organic photodetectors working at forward and reverse bias

Abstract: It is a great challenge to obtain narrowband and photomultiplication (PM) type organic photodetectors (OPDs) without optical filters due to the broad absorption range and large exciton binding energy of organic materials. Narrowband OPDs with the special structure of ITO/PFN-OX/P3HT : PC61BM (100 : 1,wt/wt)/Al were successfully fabricated with different active layer thicknesses, exhibiting a tunable response window and PM phenomenon under bi-directional bias. The OPDs exhibit U-shaped EQE spectra with two narrowband response windows under forward bias and a single narrowband response window under reverse bias. The best EQE of the optimized OPDs with a 4.0 μm thick active layer approaches 7160% or 8180% for 340 nm or 650 nm light illumination at 60 V and 1640% for 665 nm light illumination at −60 V, respectively. The most important features of the optimized OPDs is that the full width at half-maximum (FWHM) of their response windows is less than 30 nm under bi-directional biases, which can be well maintained at large bias. The PM type narrowband OPDs working at bi-directional bias are the first to be reported with a tunable response range, further indicating that the density of the electrons trapped in PC61BM near the hole injection electrode plays the key role in determining the interfacial band bending for hole tunneling injection from the external circuit.

Highly Crumpled All-Carbon Transistors for Brain Activity Recording

Abstract: Neural probes based on graphene field-effect transistors have been demonstrated. Yet, the minimum detectable signal of graphene transistor-based probes is inversely proportional to the square root of the active graphene area. This fundamentally limits the scaling of graphene transistor-based neural probes for improved spatial resolution in brain activity recording. Here, we address this challenge using highly crumpled all-carbon transistors formed by compressing down to 16% of its initial area. All-carbon transistors, chemically synthesized by seamless integration of graphene channels and hybrid graphene/carbon nanotube electrodes, maintained structural integrity and stable electronic properties under large mechanical deformation, whereas stress-induced cracking and junction failure occurred in conventional graphene/metal transistors. Flexible, highly crumpled all-carbon transistors were further verified for in vivo recording of brain activity in rats. These results highlight the importance of advanced ma...

High-Quality Monolithic Graphene Films via Laterally Stitched Growth and Structural Repair of Isolated Flakes for Transparent Electronics

Abstract: Exfoliation of graphene flakes in solution is a high-yield and low-cost synthesis method, but the quality of the obtained graphene flakes is not high, because of the presence of functional groups and structural defects. Therefore, the ability to synthesize high-quality graphene with excellent electrical properties is desirable for electronic applications. Here, we present a facile and rapid annealing approach with nickel for structural repair in isolated graphene flakes on rough insulating substrates, accompanied by lateral stitching of the isolated parts to form a continuous and monolithic film. This process involves the active carbon species being coalesced at the desaturation edge of graphene flakes. Meanwhile, the defects in graphene can be also repaired to improve its crystal quality and electrical properties. Significantly, the carrier mobility of graphene with excellent structural properties is >1000 cm2 V–1 s–1 on average, nearly 10 times higher than that of the process with copper or 100 times hi...

Implantable flexible neural microelectrode comb, and preparation method and implantation method therefor

Abstract: Disclosed are an implantable flexible neural microelectrode comb, and a preparation method and implantation method therefor. The flexible neural microelectrode comb is mainly composed of a flexible substrate layer (1), a flexible insulation layer (2), and a metal connection wire layer (3) arranged between the flexible substrate layer (1) and the flexible insulation layer (2); the flexible neural microelectrode comb comprises a filament structure (4), a mesh structure (5), a plane structure (6) and a bonding pad area (7) connected in sequence; electrode sites (8) are arranged on the filament structure (4); bonding pads are arranged on the bonding pad area (7); the metal connection wire layer (3) is composed of metal connection wires connecting the electrode sites (8) and the bonding pads; and the flexible insulation layer (2) is not arranged on the surfaces of the electrode sites (8) and the bonding pads. The prepared flexible neural microelectrode comb has a structure gradually changing from a filament to a mesh to a plane structure, thus improving mechanical stability during a deformation process. The mechanical properties of the implantable flexible neural microelectrode comb match brain tissue, the implantation footprint is small, an inflammatory response of the brain is avoided, and electrophysiological signals in the brain can be stably tracked and measured in a multi-site manner for a long time.

Ultramicroelectrode array modified with magnetically labeled Bacillus subtilis , palladium nanoparticles and reduced carboxy graphene for amperometric determination of biochemical oxygen demand

Abstract: The authors describe a microsensor for the determination of biochemical oxygen demand. Different from established BOD detection schemes that incorporate a film of immobilized microbes, the sensitive element of this BOD microsensor consists of magnetite-functionalized Bacillus subtilis that can be immobilized and regenerated on an ultramicroelectrode array (UMEA). Modification and regeneration are magnetically controlled. The oxygen consumed is amperometrically quantified by using an UMEA modified with palladium nanoparticles and reduced carboxy graphene. The assay can be performed within 5 min owing to the fast mass transfer of the magnetite-functionalized microbes on the surface of the UMEA. The calibration plot, best acquired at a voltage of -0.4 V vs. Ag/AgCl, is linear in the 2 to 15 mg⋅L−1 BOD concentration range. A critical comparison with other BOD sensor shows the sensitivity of this sensor to be largely improved. It was successful applied to the determination of BOD in spiked water samples.