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Journal ArticleDOI

High-Performance Broadband Photo-Detection in Solution-Processed ZnO-ZnCr 2 O 4 Nanowalls

TL;DR: In this paper, the authors demonstrate high performance broadband UV-to-NIR detection, which is a critical issue associated with ZnO-based photodetectors, using an as-synthesized ZnNO-ZnCr2O4 nanowalls.
Abstract: We demonstrate high performance broadband UV-to-NIR detection, which is a critical issue associated with ZnO-based photodetectors. The as-synthesized ZnO-ZnCr2O4 nanowalls were first time utilized for broadband, i.e., 250–850 nm photo-detection (both in front and back illumination configurations). The dark current was found to be as low as 0.12 nA. The device has shown peak sensitivity for the UV region ( $\lambda _{\mathrm {ex}}= {350}$ nm) with the photo-sensitivity of $\sim 1.28\times 10^{5}$ , photo-responsivity of 5.49 AW−1, photo-detectivity of $1.91\times 10^{13}$ cmHz1/2W−1, linear dynamic range of 82 dB, and external quantum efficiency of 1900%. In addition, the white light emission (CIE coordinates of 0.32 and 0.34) was also observed in the ZnO-ZnCr2O4 nanowalls. This letter will open new directions in oxide semiconductors-based optoelectronic devices.
Citations
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Journal ArticleDOI
TL;DR: In this article, the bandgap of CuO (p-type semiconductor) has been engineered from an indirect band gap of ∼1ÕeV to a direct band-gap of 4Õ eV just by tuning the nanostructure morphology and midgap defect states.
Abstract: In this work, the bandgap of CuO (p-type semiconductor) has been engineered from an indirect bandgap of ∼1 eV to a direct bandgap of 4 eV just by tuning the nanostructure morphology and midgap defect states. The absorption in near-infrared (NIR) and visible regions is ordinarily suppressed by controlling the growth parameters. Considering the increasing scope and demand of varying spectral range (UV-C to NIR) photodetectors, the systematic variation of the available density of states (DOS) at a particular energy level in CuO nanostructures has been utilized to fabricate dual-band (250 nm and 900 nm), broadband (250 nm–900 nm), and UV-C (250 nm) photodetectors. The sensitivity and detectivity of the photodetector for broadband detectors were ∼103 and 2.24 × 1011 Jones for the wavelengths of 900 nm and 122 and 2.74 × 1010 Jones for 250 nm wavelength light, respectively. The UV-C detector showed a sensitivity of 1.8 and a detectivity of 4 × 109 Jones for 250 nm wavelength light. A plausible mechanism for the photoconduction has been proposed for explaining the device operation and the effect of variation in available DOS. The obtained photodetectors are the potential candidates for future optoelectronic applications.

38 citations

Journal ArticleDOI
TL;DR: In this article, a solar-blind photo-detection using highly transparent CuO nanostructures (with a bandgap of 4.15 eV) has been demonstrated.
Abstract: High-performance solar-blind photo-detection using highly transparent CuO nanostructures (with a bandgap of 4.15 eV) has been demonstrated. The device shows the dark current as low as 0.2 nA (−10 V applied bias) and no signature of breakdown even at a bias up to ±175 V. The device has shown record photo-sensitivity of 610, photo-responsivity of 14.02 A/W and photo-detectivity of $3.59\times 10 ^{13}$ cmHz 1/2W−1 in the UV-C region. The ratio of photo-responsivities at 210 nm and 500 nm i.e. R210/R500 was found to be $5.05\times 10 ^{4}$ . Additionally, the device has shown external quantum efficiency of ~5900 % at 210 nm excitation. This letter will establish CuO as one of the most promising ultra-wide bandgap semiconductors for cost-effective solar blind photo-detection.

11 citations


Cites background from "High-Performance Broadband Photo-De..."

  • ...Typically, LDR is defined as: (LDR = 20log I ∗ ph Id ), where Id is the current in the dark state, and Iph is the photocurrent, calculated at 1 mW/cm2 incident light intensity [22]....

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Journal ArticleDOI
TL;DR: In this article, the In2O3 vertical nanostructures (VNS) are fabricated using a glancing angle deposition (GLAD) technique upon an In 2O3 thin film (TF) on a n-type silicon (n-Si) substrate.
Abstract: In2O3 vertical nanostructures (VNS) are fabricated using a glancing angle deposition (GLAD) technique upon an In2O3 thin film (TF) on a n-type silicon (n-Si) substrate. Analysis using high-resolution transmission electron microscopy (HRTEM) and high-resolution x-ray diffraction (HRXRD) revealed that the In2O3 VNS are amorphous in nature. An average ~4.5-fold enhancement in absorption was observed and a microscopic origin was proposed for observed bandgap changes for the n-Si/In2O3 TF/GLAD In2O3 VNS and bare n-Si/In2O3 TF samples in the visible region due to surface-related trap states or oxygen vacancies. The improvement in photodetection was attributed to the presence of a large number of surface-related trap states at the edge of metal contacts. The fabricated VNS detector possesses enhanced photosensitivity (~1.7-fold) due to an efficient photogating effect in the depletion region. A maximum detectivity of ~12.8 × 107 Jones was observed for the n-Si/In2O3 TF/GLAD In2O3 VNS device, which possesses ~15.6-fold enhanced detectivity as compared to the bare n-Si/In2O3 TF device.

9 citations

Journal ArticleDOI
TL;DR: In this article, bipolar phototransistors based on wide bandgap organic-inorganic semiconductor bilayer structure are designed for broadband optical detection through purposeful material selection and band matching, the energy level difference of heterojunction interface is obtained to promote photoinduced charge separation and realize optical detection from ultraviolet to near-infrared.
Abstract: In this letter, bipolar phototransistors based on wide bandgap organic-inorganic semiconductor bilayer structure are designed for broadband optical detection. Through purposeful material selection and band matching, the energy level difference of heterojunction interface is obtained to promote photo-induced charge separation and realize optical detection from ultraviolet to near-infrared. Via the suppression of dark current by field effect regulation, the phototransistors demonstrate high normalized detectivity (1014 – 1015 jones). The diversity of organic semiconductor materials provides a wide range of choices to realize broadband detection by the band matching with inorganic semiconductor materials.

4 citations

References
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Journal ArticleDOI
TL;DR: Despite the slow relaxation time, the extremely high internal gain of ZnO NW photodetectors results in gain-bandwidth products higher than approximately 10 GHz, which promise a new generation of phototransistors for applications such as sensing, imaging, and intrachip optical interconnects.
Abstract: ZnO nanowire (NW) visible-blind UV photodetectors with internal photoconductive gain as high as G ∼ 108 have been fabricated and characterized. The photoconduction mechanism in these devices has been elucidated by means of time-resolved measurements spanning a wide temporal domain, from 10-9 to 102 s, revealing the coexistence of fast (τ ∼ 20 ns) and slow (τ ∼ 10 s) components of the carrier relaxation dynamics. The extremely high photoconductive gain is attributed to the presence of oxygen-related hole-trap states at the NW surface, which prevents charge-carrier recombination and prolongs the photocarrier lifetime, as evidenced by the sensitivity of the photocurrrent to ambient conditions. Surprisingly, this mechanism appears to be effective even at the shortest time scale investigated of t < 1 ns. Despite the slow relaxation time, the extremely high internal gain of ZnO NW photodetectors results in gain-bandwidth products (GB) higher than ∼10 GHz. The high gain and low power consumption of NW photodetec...

2,448 citations


"High-Performance Broadband Photo-De..." refers background in this paper

  • ...In general, a depletion region is getting created near to surface due to adsorption of O2 [19]....

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Journal ArticleDOI
25 Sep 2009-Science
TL;DR: This work demonstrates polymer photodetectors with broad spectral response fabricated by using a small-band-gap semiconducting polymer blended with a fullerene derivative that can exceed the response of an inorganic semiconductor detector at liquid helium temperature.
Abstract: Sensing from the ultraviolet-visible to the infrared is critical for a variety of industrial and scientific applications. Today, gallium nitride-, silicon-, and indium gallium arsenide--based detectors are used for different sub-bands within the ultraviolet to near-infrared wavelength range. We demonstrate polymer photodetectors with broad spectral response (300 to 1450 nanometers) fabricated by using a small-band-gap semiconducting polymer blended with a fullerene derivative. Operating at room temperature, the polymer photodetectors exhibit detectivities greater than 10(12) cm Hz(1/2)/W and a linear dynamic range over 100 decibels. The self-assembled nanomorphology and device architecture result in high photodetectivity over this wide spectral range and reduce the dark current (and noise) to values well below dark currents obtained in narrow-band photodetectors made with inorganic semiconductors.

1,580 citations


"High-Performance Broadband Photo-De..." refers methods in this paper

  • ...Linear dynamic range (LDR) = 20log I ∗ ph Id (where, Id is the dark current and Iph is the maximum photocurrent, measured at light intensity of 1 mW/cm2) was calculated for the device (which is range of current over which the response is linear) and the value was found to be nearly 82 dB, which is better than previously reported devices using ZnO [20], [21]....

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Journal ArticleDOI
TL;DR: This Review surveys the uniqueness and universality of MOs versus other unconventional electronic materials in terms of materials chemistry and physics, electronic characteristics, thin-film fabrication strategies and selected applications in thin- film transistors, solar cells, diodes and memories.
Abstract: Optical transparency, tunable conducting properties and easy processability make metal oxides key materials for advanced optoelectronic devices. This Review discusses recent advances in the synthesis of these materials and their use in applications. Metal oxides (MOs) are the most abundant materials in the Earth's crust and are ingredients in traditional ceramics. MO semiconductors are strikingly different from conventional inorganic semiconductors such as silicon and III–V compounds with respect to materials design concepts, electronic structure, charge transport mechanisms, defect states, thin-film processing and optoelectronic properties, thereby enabling both conventional and completely new functions. Recently, remarkable advances in MO semiconductors for electronics have been achieved, including the discovery and characterization of new transparent conducting oxides, realization of p-type along with traditional n-type MO semiconductors for transistors, p–n junctions and complementary circuits, formulations for printing MO electronics and, most importantly, commercialization of amorphous oxide semiconductors for flat panel displays. This Review surveys the uniqueness and universality of MOs versus other unconventional electronic materials in terms of materials chemistry and physics, electronic characteristics, thin-film fabrication strategies and selected applications in thin-film transistors, solar cells, diodes and memories.

1,098 citations


"High-Performance Broadband Photo-De..." refers background in this paper

  • ...Oxide semiconductors have shown tremendous potential for the next generation photodetectors due to their ease of processing, better performance and options for the tunability of functional properties [2]....

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Journal ArticleDOI
TL;DR: A series of Cr(3+)-doped zinc gallogermanate NIR persistent phosphors that exhibit strong emission at 650-1,000 nm, extending beyond the typical 690-750 nm, and with a super-long afterglow of more than 360 h are reported.
Abstract: Visible-light persistent phosphors are being widely used as self-sustained night-vision materials because of their sufficiently strong and long afterglow (>10 h) and their ability to be excited by sunlight as well as room light. In contrast, persistent phosphors for near-infrared (NIR) wavelengths are lacking. Here we report a series of Cr(3+)-doped zinc gallogermanate NIR persistent phosphors that exhibit strong emission at 650-1,000 nm, extending beyond the typical 690-750 nm, and with a super-long afterglow of more than 360 h. These new NIR persistent phosphors are all-weather materials that can be rapidly, effectively and repeatedly charged by natural sunlight in almost all kinds of outdoor environment. Seconds to minutes of sunlight activation can result in more than two weeks of persistent NIR light emission. This new series of NIR persistent materials have potential applications in night-vision surveillance, solar energy utilization and in vivo bio-imaging.

1,034 citations


"High-Performance Broadband Photo-De..." refers background in this paper

  • ...transitions of Cr3+ includes the 290 nm and 320 nm band originating from the (4)A2 (4F) → (4)T1 (4P) (te2) transition, the 425 nm transition belongs to (4)A2 (4F) → (4)T1 (4F) (t2e) [17], [18]....

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Journal ArticleDOI
TL;DR: The sensing response of Au-ZnO nancomposite is enhanced both in UV and visible region, as compared to control ZnO, and the sensitivity is observed to be higher in the visible region due to the LSPR effect of Au NPs.
Abstract: In this study we report the enhancement of UV photodetection and wavelength tunable light induced NO gas sensing at room temperature using Au-ZnO nanocomposites synthesized by a simple photochemical process Plasmonic Au-ZnO nanostructures with a size less than the incident wavelength have been found to exhibit a localized surface plasmon resonance (LSPR) that leads to a strong absorption, scattering and local field enhancement The photoresponse of Au-ZnO nanocomposite can be effectively enhanced by 80 times at 335 nm over control ZnO We also demonstrated Au-ZnO nanocomposite's application to wavelength tunable gas sensor operating at room temperature The sensing response of Au-ZnO nancomposite is enhanced both in UV and visible region, as compared to control ZnO The sensitivity is observed to be higher in the visible region due to the LSPR effect of Au NPs The selectivity is found to be higher for NO gas over CO and some other volatile organic compounds (VOCs), with a minimum detection limit of 01 ppb for Au-ZnO sensor at 335 nm

340 citations


"High-Performance Broadband Photo-De..." refers background in this paper

  • ...based devices (summarized in Table 1) [6], [8], [9], [22]–[28]....

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  • ...In case of metal coated ZnO the performance in visible region has shown limited success [9]....

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