Solution-Processed Transparent CuO Thin Films for Solar-Blind Photodetection
TL;DR: In this paper, a solution-processed thin films of CuO with a direct bandgap of 3.87 eV were first time utilized for solar blind photo-detection.
Abstract: Highly transparent (Transmittance >90%), solution-processed thin films of CuO with a direct bandgap of 3.87 eV were first time utilized for solar blind photo-detection. The CuO thin-film-based photodetector has shown very large DUV/Vis. rejection ratio of ~5430. The device has shown photo-responsivity value of 7.77 AW $^{-\textsf {1}}$ and photo-detectivity of $3.08\times 10^{\textsf {11}}$ cm $\cdot $ Hz $^{\textsf {1/2}}\cdot \text{W}^{-\textsf {1}}$ . Interestingly, the device has shown persistent photoconductivity with a retention time of several days. In order to use the device for optical memory, the reset mechanism has been successfully demonstrated by annealing the device at 50 °C. The developed solution processed, highly transparent, solar-blind photodetector has immense potential for next-generation cost-effective optoelectronic devices.
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TL;DR: These findings provide a route to fabricate high performance and wide detection range p-type metal oxide photodetectors and show the optimal response in the near-infrared region, owing to the high absorption coefficient.
Abstract: Photodetectors based on p-type metal oxides are still a challenge for optoelectronic device applications. Many effects have been paid to improve their performance and expand their detection range. Here, high-quality Cu1-xNixO (x = 0, 0.2, and 0.4) film photodetectors were prepared by a solution process. The crystal quality, morphology, and grain size of Cu1-xNixO films can be modulated by Ni doping. Among the photodetectors, the Cu0.8Ni0.2O photodetector shows the maximum photocurrent value (6 × 10-7 A) under a 635 nm laser illumination. High responsivity (26.46 A/W) and external quantum efficiency (5176%) are also achieved for the Cu0.8Ni0.2O photodetector. This is because the Cu0.8Ni0.2O photosensitive layer exhibits high photoconductivity, low surface states, and high crystallization after 20% Ni doping. Compared to the other photodetectors, the Cu0.8Ni0.2O photodetector exhibits the optimal response in the near-infrared region, owing to the high absorption coefficient. These findings provide a route to fabricate high-performance and wide-detection range p-type metal oxide photodetectors.
41 citations
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
TL;DR: In this paper, a dual-functional smart window that can detect outdoor UV intensity in real time and then respond by automatically adjusting its color to control UV transmission has been developed for the first time by integrating a TiO2 based photodetector with a viologen hydrogel based electrochromic device.
Abstract: Excessive ultraviolet (UV) radiation is known to cause several skin diseases, and hence smart electronics with the capacity to measure and control UV radiation have attracted substantial attention. In this work, a dual-functional smart window that can detect outdoor UV intensity in real time and then respond by automatically adjusting its color to control UV transmission has been developed for the first time by integrating a TiO2 based photodetector with a viologen hydrogel based electrochromic device. Excellent photodetector properties, including high transparency of 90% at 585 nm, great photoresponsivity of 67.15 mA W−1 and an outstanding photo-dark current ratio of 1.48 × 104 have been demonstrated. Meanwhile, the viologen hydrogel based electrochromic device possesses a significant color change with modulation of transmittance up to 60% in the visible range and can efficiently block almost 94% radiation in the UV-A range. This work demonstrates the ability of real time monitoring and regulating the UV radiation via integration of TiO2 films with electrochromic hydrogels, which may guide the development of next generation multifunctional smart windows.
28 citations
TL;DR: In this paper, the authors reported the synthesis of copper oxide (CuO) thin films by sol-gel process assisted by spin coating technique at room temperature using a spectrophotometer (UV-vis-NIR) in a range of 300−1100
15 citations
TL;DR: In this article, the I-V characteristics of all the deposited CuO samples were investigated and the CuO-100 dip cycle thin film is found to have a lower ideality factor of 5.4.
Abstract: CuO thin films deposited using SILAR coating technique with various dip-cycles. The prepared thin films were characterized to elucidate the structural and morphological features using analytical techniques such as XRD and SEM, respectively. It was found that along with the thickness of CuO films, the crystallinity and morphology of the deposited films have changed appreciably. The optical, electrical, and photosensing properties were also studied for deposited films. The optical and electrical properties for the thin film prepared with 100 dip-cycles were found best as compared to 50, 75, 125 dip-cycles, this may be due to improved crystallinity and uniform distribution of nanoclusters over the substrate. From the UV absorption studies, it was found that the CuO-100 thin-film has the highest absorption and a low bandgap of 1.67 eV. Also, the CuO with 100 dip sample exhibits a minimum resistivity of 2.98 × 102 Ω cm that leads to a higher carrier concentration of 4.63 × 1013 cm−3 and mobility of 4.53 cm2V−1 s−1. The I–V characteristics of all the deposited CuO samples were investigated and the CuO-100 dip cycle thin film is found to have a lower ideality factor of 5.4. Additionally, the Cu-100 thin film reveals a high responsivity and external quantum efficiency values of 1.67 × 10−1 A/W and 54%, respectively. Thus, in the SILAR dip-coating technique, the dipping cycles influence the CuO formation as well as their properties.
14 citations
References
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TL;DR: In this paper, a general review of the advances in widebandgap semiconductor photodetectors is presented, including SiC, diamond, III-nitrides and ZnS.
Abstract: Industries such as the automotive, aerospace or military, as well as environmental and biological research have promoted the development of ultraviolet (UV) photodetectors capable of operating at high temperatures and in hostile environments. UV-enhanced Si photodiodes are hence giving way to a new generation of UV detectors fabricated from wide-bandgap semiconductors, such as SiC, diamond, III-nitrides, ZnS, ZnO, or ZnSe. This paper provides a general review of latest progresses in wide-bandgap semiconductor photodetectors.
1,194 citations
"Solution-Processed Transparent CuO ..." refers background in this paper
...Wide band gap oxide semiconductors are potential contenders for solar blind photodetectors [7], [8]....
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TL;DR: A comprehensive review of recent synthetic methods along with associated synthesis mechanisms, characterization, fundamental properties, and promising applications of Cupric oxide (CuO) nanostructures is presented in this article.
1,030 citations
"Solution-Processed Transparent CuO ..." refers background or result in this paper
...98 eV and in well resemblance with previously reported values [24], [27]....
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...Three different peaks were observed at 275 cm−1, 323 cm−1 and 640 cm−1, which can be assigned to A(1)g, B 1 g and B 2 g modes of CuO, respectively [24]....
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TL;DR: In this paper, the authors focused on the perspective of molding devices through exploring new materials and novel architectures inspired by state-of-the-art UV photodetectors.
594 citations
"Solution-Processed Transparent CuO ..." refers background in this paper
...have been demonstrated for solar blind detection [3]–[5]....
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TL;DR: In this article, the anion vacancies in II-VI and chalcopyrite semiconductors were identified as a class of intrinsic defects that can exhibit metastable behavior.
Abstract: Using first-principles electronic structure calculations we identify the anion vacancies in II-VI and chalcopyrite $\mathrm{Cu}\text{\ensuremath{-}}\mathrm{III}\text{\ensuremath{-}}{\mathrm{VI}}_{2}$ semiconductors as a class of intrinsic defects that can exhibit metastable behavior. Specifically, we predict persistent electron photoconductivity ($n$-type PPC) caused by the oxygen vacancy ${V}_{\mathrm{O}}$ in $n$-ZnO, originating from a metastable shallow donor state of ${V}_{\mathrm{O}}$. In contrast, we predict persistent hole photoconductivity ($p$-type PPC) caused by the Se vacancy ${V}_{\mathrm{Se}}$ in $p\text{\ensuremath{-}}{\mathrm{CuInSe}}_{2}$ and $p\text{\ensuremath{-}}{\mathrm{CuGaSe}}_{2}$. We find that ${V}_{\mathrm{Se}}$ in the chalcopyrite materials is amphoteric having two ``negative-$U$''-like transitions, i.e., a double-donor transition $\ensuremath{\epsilon}(2+∕0)$ close to the valence band and a double-acceptor transition $\ensuremath{\epsilon}(0∕2\ensuremath{-})$ closer to the conduction band. We introduce a classification scheme that distinguishes two types of defects: type $\ensuremath{\alpha}$, which have a defect-localized-state (DLS) in the band gap, and type $\ensuremath{\beta}$, which have a resonant DLS within the host bands (e.g., the conduction band for donors). In the latter case, the introduced carriers (e.g., electrons) relax to the band edge where they can occupy a perturbed-host state. Type $\ensuremath{\alpha}$ is nonconducting, whereas type $\ensuremath{\beta}$ is conducting. We identify the neutral anion vacancy as type $\ensuremath{\alpha}$ and the doubly positively charged vacancy as type $\ensuremath{\beta}$. We suggest that illumination changes the charge state of the anion vacancy and leads to a crossover between $\ensuremath{\alpha}$- and $\ensuremath{\beta}$-type behavior, resulting in metastability and PPC. In ${\mathrm{CuInSe}}_{2}$, the metastable behavior of ${V}_{\mathrm{Se}}$ is carried over to the $({V}_{\mathrm{Se}}\text{\ensuremath{-}}{V}_{\mathrm{Cu}})$ complex, which we identify as the physical origin of PPC observed experimentally. We explain previous puzzling experimental results in ZnO and ${\mathrm{CuInSe}}_{2}$ in the light of this model.
551 citations
Additional excerpts
...413 eV) calculations (not shown here) [14], [33], [34]....
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TL;DR: Detailed Cu 2p, Cu LVV, O 1s and O KLL spectra are reported which are in good agreement with previous results and are mainly due to modifications of the 3d and O 2p electron configurations.
Abstract: The electronic and optical properties of Cu, CuO and Cu(2)O were studied by x-ray photoelectron spectroscopy (XPS) and reflection electron energy-loss spectroscopy (REELS). We report detailed Cu 2p, Cu LVV, O 1s and O KLL spectra which are in good agreement with previous results. REELS spectra, recorded for primary energies in the range from 150 to 2000 eV, were corrected for multiple inelastically scattered electrons to determine the effective inelastic scattering cross section. The dielectric functions and optical properties were determined by comparing the experimental inelastic electron scattering cross section with a simulated cross section calculated within the semi-classical dielectric response model in which the only input is Im(-1/e) by using the QUEELS-e(k,ω)-REELS software package. By Kramers-Kronig transformation of the determined Im(-1/e), the real and imaginary parts (e(1) and e(2)) of the dielectric function, and the refractive index n and extinction coefficient k were determined for Cu, CuO, and Cu(2)O in the 0-100 eV energy range. Observed differences between Cu, CuO and Cu(2)O are mainly due to modifications of the 3d and O 2p electron configurations.
419 citations
"Solution-Processed Transparent CuO ..." refers background or methods in this paper
...The most common technique to grow CuO thin films/nanostructures involves annealing of Cu foil at 500 °C in oxygen environment[17], [18]....
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...films/nanostructures but, in general these are complex and require high temperature processing [16], [17]....
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