Transparent integrated pyroelectric-photovoltaic structure for photo-thermo hybrid power generation.

Thermal losses in photoelectric devices limit their energy conversion efficiency, and cyclic input of energy coupled with pyroelectricity can overcome this limit. Here, incorporating a pyroelectric absorber into a photovoltaic heterostructure device enables efficient electricity generation by leveraging spontaneous polarization based on pulsed light-induced thermal changes. The proposed pyroelectric-photovoltaic device outperforms traditional photovoltaic devices by 2.5 times due to the long-range electric field that occurs under pulse illumination. Optimization of parameters such as pulse frequency, scan speed, and illumination wavelength enhances power harvesting, as demonstrated by a power conversion efficiency of 11.9% and an incident-photon-to-current conversion efficiency of 200% under optimized conditions. This breakthrough enables reconfigurable electrostatic devices and presents an opportunity to accelerate technology that surpasses conventional limits in energy generation.

Van Der Waals Semiconductor Based Omnidirectional Bifacial Transparent Photovoltaic for Visual-Speech Photocommunication.

Omnidirectional photosensing is crucial in optoelectronic devices, enabling a wide field of view (wFoV) and leveraging potential applications for the Internet of Things in sensors, light fidelity, and photocommunication. The wFoV helps overcome the limitations of line-of-sight communication, and transparent photodetection becomes highly desirable as it enables the capture of optical information from various angles. Therefore, developing a photoelectric device with a 360° wFoV, ultra sensitivity to photons, power generation, and transparency is of utmost importance. This study utilizes a heterojunction of van der Waals SnS with Ga2 O3 to fabricate a transparent photovoltaic (TPV) device showing a 360° wFoV with bifacial onsite power production. SnS/Ga2 O3 heterojunction preparation consists of magnetron sputtering and is free from nanopatterning/nanostructuring to achieve the desired wFoV window device. The device exhibits a high average visible transmittance of 56%, generates identical power from bifacial illumination, and broadband fast photoresponse. Careful analysis of the device shows an ultra-sensitive photoinduced defect-modulated heterojunction and photocapacitance, revealed by the impedance spectroscopy, suggesting photon-flux driven charge diffusion. Leveraging the wFoV operation, the TPV embedded visual and speech photocommunication prototype demonstrated, aiming to help visually and auditory impaired individuals, promising an environmental-friendly sustainable future.

Field-Induced Transparent Electrode-Integrated Transparent Solar Cells and Heater for Active Energy Windows: Broadband Energy Harvester.

Invisible power generation by natural and artificial light enables sustainability by onsite-power deployment, lower cost, and minimal burden on the built environment. However, dark, opaque photovoltaics limit light utilization in a transparent way. Herein, it is proposed that the active energy window (AEW) invisibly features power production, providing higher freedom for onsite power generators in window objects without limiting human vision. The AEW has a transparent photovoltaic (TPV) for onsite power and a transparent heater (TH) to remove the effects of shadows from snow and recover the power lost. Moreover, a heating function is applied to remove the effects of weathering related to snow. The proposed prototype integrates a TPV-TH, offering ultraviolet (UV)-blocking, daylighting, thermal comfort, and onsite power with a power conversion efficiency of 3% (AM1.5G). Field-induced transparent electrodes are applied to the TPV-TH and designed considering the AEW. Owing to these electrodes, the AEW ensure a wide field-of-view without optical dead zones, ensuring see-through vision. The first TPV-TH integration is performed into a 2 cm2 -window that generates onsite power of 6 mW and has an average visible transmittance of ≈39%. It is believed that light can be utilized with comfort through the AEW in self-sustainable buildings and vehicles.

All-Oxide Transparent Photodetector Array for Ultrafast Response through Self-Powered Excitonic Photovoltage Operation.

Can photodetectors be transparent and operate in self-powered mode? Is it possible to achieve invisible electronics, independent of the external power supply system, for on-site applications? Here, a ZnO/NiO heterojunction-based high-functional transparent ultraviolet (UV) photodetector operating in the self-powered photovoltaic mode with outstanding responsivity and detectivity values of 6.9 A W-1 and 8.0 × 1012 Jones, respectively, is reported. The highest IUV /Idark value of 8.9 × 104 is attained at a wavelength of 385 nm, together with a very small dark current value of 9.15 × 10-12 A. A large-scale sputtering method is adopted to deposit the heterostructure of n-ZnO and p-NiO sequentially. This deposition instinctively forms an abrupt junction, resulting in a high-quality heterojunction device. Moreover, developing a ZnO/NiO-heterojunction-based 4 × 5 matrix array with an output photovoltage of 4.5 V is preferred for integrating photodetectors into sensing and imaging systems. This transparent UV photodetector exhibits the fastest photo-response time (83 ns) reported for array configurations, which is achieved using an exciton-induced photovoltage based on a neutral donor-bound exciton. Overall, this study provides a simple method for achieving a high-performance large-scale transparent UV photodetector with a self-powered array configuration.

Highly Transparent Bidirectional Transparent Photovoltaics for On-Site Power Generators.

If we can transparently produce energy, we may apply invisible power generators to residential architectures to supply energy without losing visibility. Transparent photovoltaic cells (TPVs) are a transparent solar technology that transmits visible light while absorbing the invisible short wavelengths, such as ultraviolet. Installing TPVs in buildings provides an on-site energy supply platform as a window-embedded power generator or color-matched solar cell installation on a building surface. The record-high power generation (10.82 mW) and photocurrent value (68.25 mA) were achieved from large-scale TPVs (25 cm2). The metal oxide heterojunction is the fundamental TPV structure. The high-performance TPVs were achieved by adopting a thin Si film between ZnO and NiO as a functional light-absorbing layer. Based on the large energy band gap of metal oxides, TPVs have a clear transmittance (43%) and good color coordinates, which ensure degrees of freedom to adopt TPV power generators in various colored structures or transparent power windows. The bidirectional feature of TPVs is ultimately desirable to maximize light utilization. TPVs can generate electric power from sunlight during the day and can also work from artificial light sources at night. In the near future, humans will acquire electric power without losing visibility with on-site energy supply platforms.

Transparent Photovoltaics for Self-Powered Bioelectronics and Neuromorphic Applications.

Inspired by the brain, future computation depends on creating a neuromorphic device that is energy-efficient for information processing and capable of sensing and learning. The current computation-chip platform is not capable of self-power and neuromorphic functionality; therefore, a need exists for a new platform that provides both. This Perspective illustrates potential transparent photovoltaics as a platform to achieve scalable, multimodal sensory, self-sustainable neural systems (e.g., visual cortex, nociception, and electronic skin). We present herein a strategy to harvest solar power using a transparent photovoltaic device that provides neuromorphic functionality to implement versatile, sustainable, integrative, and practical applications. The proposed solid-inorganic heterostructure platform is indispensable for achieving a variety of biosensors, sensory systems, neuromorphic computing, and machine learning.

Transparent photovoltaic memory for neuromorphic device.

Bio-inspired electronic devices have significant potential for use in memory devices of the future, including in the context of neuromorphic computing and architecture. This study proposes a transparent heterojunction device for the artificial human visual cortex. Owing to their high transparency, such devices directly react to incoming light to mimic neurological and biological processes in the nervous system. Metal-oxide materials are applied to form a transparent heterojunction (n-type ZnO/p-type NiO) in the proposed device that also provides the photovoltaic function to realize the optic nerve system. The device also exhibits nociceptive features. Its transparent photovoltaic feature endows it with self-powered operation that ensures long-term reliability without needing to replace the power system. This self-powered and highly transparent visual electronic device can provide a route for sustainable applications of neuromorphic computing, including artificial eyes.

Transparent Stacked Photoanodes with Efficient Light Management for Solar-Driven Photoelectrochemical Cells.

Solar-driven hydrogen generation is one of the most promising approaches for building a sustainable energy system. Photovoltaic-assisted photoanodes can help to reduce the overpotential of water splitting in photoelectrochemical (PEC) cells. Transparent photoanodes can improve light-conversion efficiency by absorbing high-energy photons while transmitting lower energy photons to the photocathode for hydrogen production. In this work, transparent photoanodes were implemented by forming metal-oxide junctions of NiO/TiO2 heterostructures for creating the photovoltaic effect. The photovoltaic-induced transparent photoelectrode (PTPE) provides the photovoltage (0.7 V), which efficiently reduces the onset potential voltage by -0.38 V versus the reversible hydrogen electrode (RHE), as compared to 0.17 V versus RHE for a single-TiO2 photoanode. The PEC cell has a high photocurrent of 1.68 mA at 1.23 V with respect to the RHE. The chemical endurance of metal-oxides maintains the stability of the PTPE for over 100 h in an alkaline electrolyte of 0.1 M KOH. The results of this study reveal that combining multiple PTPE cells to create a stacked photoanode enhances the photocurrent roughly in proportion to the number of PTPE cells. This design scheme for optimizing the light-conversion efficiency in a PTPE-photoanode system is promising for creating robust systems for on-site energy producers.

Broadband photoresponse data of transparent all-oxide photovoltaics of ZnO/NiO.

In this data article, the properties of all transparent metal oxide of ZnO/NiO heterostructure "Transparent all-oxide photovoltaics and broadband high-speed energy-efficient optoelectronics" [1] are presented by characteristics of ZnO and NiO layers, open circuit voltage decay (OCVD), broadband light with intensity dependent current-voltage plots. The device performances under the effect of various optical excitation of intermediated-band, bound excitonic, free-excitonic and band-to-band are presented. The ZnO/NiO heterostructure direction grown on ITO/glass substrate by large area sputtering method [1] was characterized by UV-visible plots and scanning electron microscope (SEM). Carrier lifetime using OCVD of ZnO/NiO devices with carbon paint metal contact is presented. Prolonged open circuit voltage plots under UV light intensity are shown for stability and repeatability studies. I-V characteristics of ZnO/NiO heterostructure under the light wavelength from 623 nm to 365 nm are presented for energy efficient broadband optoelectronics.

Physical and chemical data of WS2 platelets and thickness-dependent photoresponses.

In this data article, the properties of WS2/ZnO type-I heterostructure which corresponds to the research article "Vertically trigonal WS2 layer embedded heterostructure for enhanced ultraviolet-visible photodetector" (Nguyen et al., 2018) are presented by characteristics of WS2 layer, diode properties, and thickness dependent photoresponses. The device performances under the effect of rapid thermal processing (RTP) is presented. The WS2 platelets grown by large area sputtering method (Nguyen et al., 2018) was characterized in term of morphology and chemical elements distribution by using transmission electron microscope (TEM), energy dispersive spectroscopy (EDS) and X-Ray photoelectron spectroscopy (XPS). Diode characterization of WS2/ZnO like rectifying ratio, ideal factor and barrier height are presented. The variation of photocurrent of ITO/WS2/ZnO/FTO/glass photodetector, its dependence on the WS2 thickness and influence of post- thermal treatment are presented.

Thickness-dependent photoelectrochemical properties of a semitransparent Co3O4 photocathode.

Co3O4 has been widely studied as a catalyst when coupled with a photoactive material during hydrogen production using water splitting. Here, we demonstrate a photoactive spinel Co3O4 electrode grown by the Kirkendall diffusion thermal oxidation of Co nanoparticles. The thickness-dependent structural, physical, optical, and electrical properties of Co3O4 samples are comprehensively studied. Our analysis shows that two bandgaps of 1.5 eV and 2.1 eV coexist with p-type conductivity in porous and semitransparent Co3O4 samples, which exhibit light-induced photocurrent in photoelectrochemical cells (PEC) containing the alkaline electrolyte. The thickness-dependent properties of Co3O4 related to its use as a working electrode in PEC cells are extensively studied and show potential for the application in water oxidation and reduction processes. To demonstrate the stability, an alkaline cell was composed for the water splitting system by using two Co3O4 photoelectrodes. The oxygen gas generation rate was obtained to be 7.17 mL·h-1 cm-1. Meanwhile, hydrogen gas generation rate was almost twice of 14.35 mL·h-1·cm-1 indicating the stoichiometric ratio of 1:2. We propose that a semitransparent Co3O4 photoactive electrode is a prospective candidate for use in PEC cells via heterojunctions for hydrogen generation.

Optical, electrical and photoresponse data of flexible and high-performing NiO/ZnO ultraviolet photodetector.

In this work, the fabrication process flow of ZnO/NiO heterojunction device on a PET substrate, optical properties, physical properties and photoresponses presented (Patel and Kim, 2017) [1]. Absorption coefficient and Tauc plots of ZnO and NiO samples are summarized. Digital photograph of flexible NiO/ZnO/ITO device on a PET substrate is presented. Surface morphologies of ITO on PET, polycrystalline ZnO on ITO/PET, and nanocrystalline NiO on ZnO/ITO/PET is presented with a demonstration of scissor-cut design. NiO/ZnO/ITO/PET photoelectric device has advantages of large-scale production and light-weight. Transmittance, reflectance and absorbance dataset of the native PET substrate (100 µm thick) is summarized. Photoresponses of the transparent (NiO/ZnO/ITO/PET) device with bias modulations including the rising edge and falling edge are included in this article.

Reproducibility analyses of photo-induced pyroelectric photodetector based on vertically grown SnS layers.

The data presented in this article includes the photograph of prepared samples and transient photoresponses for 365 and 850 nm wavelengths at different intensities. The original photographs of the working device made of vertically grown SnS layers on Si substrate are presented from the previous results (Kumar et al., 2017, 2018) [1], [2]. Reproducibility measure of the device were checked for thousands of cycles and presented with estimated parameters such as photo current density and photo+pyro current density. Data after analysis are summarized in the table, to profile the photo and pyro responses quantitatively.

Optical and electrical features of semitransparent CuO photoelectrochemical cell.

The data presented in this article are related to the research article entitled "CuO photocathode-embedded semitransparent photoelectrochemical cell" (Patel et al., 2016) [1]. This article describes the growth of Cu oxides films using reactive sputtering and application of CuO photocathode in semitransparent photoelectrochemical cell (PEC). In this data article, physical, optical and electrical properties, and PEC performances data set of the reactively sputtered semitransparent CuO samples are made publicly available to enable extended analyses.

High-performing ultrafast transparent photodetector governed by the pyro-phototronic effect.

In this work we utilized the advantage of the photo-induced pyroelectric effect - known as "Pyro-phototronic" - to design a self-powered, ultrafast, transparent ultraviolet (UV, 365 nm) photodetector. The device architecture contains an UV absorbing pyroelectric ZnO layer sandwiched between hole-selective V2O5 and a bottom ITO electrode. In addition, the device shows a high optical transmittance, >70%, in the entire visible region. The photo current of the device was enhanced from 19 to 42 µA under pulsed UV light illumination (λ = 365 nm, 4 mW cm-2) by exploiting the pyro-phototronic potential. In addition, the photodetector demonstrated ultrafast responses of ∼4 µs for the rise time and ∼16 µs for the fall time. Further, a high photoresponsivity of ∼36.34 mA W-1 and excellent photodetectivity of ∼6.04 × 1014 Jones, with an enhancement of 725% in both due to the pyroelectric potential, were measured. This novel approach will open a new path to design transparent and ultrafast devices, as well as on the flexible substrates, for future optoelectronic applications.

Growth of Wafer-Scale Standing Layers of WS2 for Self-Biased High-Speed UV-Visible-NIR Optoelectronic Devices.

This work describes the wafer-scale standing growth of (002)-plane-oriented layers of WS2 and their suitability for use in self-biased broad-band high-speed photodetection. The WS2 layers are grown using large-scale sputtering, and the effects of the processing parameters such as the deposition temperature, deposition time, and sputtering power are studied. The structural, physical, chemical, optical, and electrical properties of the WS2 samples are also investigated. On the basis of the broad-band light absorption and high-speed in-plane carrier transport characteristics of the WS2 layers, a self-biased broad-band high-speed photodetector is fabricated by forming a type-II heterojunction. This WS2/Si heterojunction is sensitive to ultraviolet, visible, and near-infrared photons and shows an ultrafast photoresponse (1.1 µs) along with an excellent responsivity (4 mA/W) and a specific detectivity (∼1.5 × 1010 Jones). A comprehensive Mott-Schottky analysis is performed to evaluate the parameters of the device, such as the frequency-dependent flat-band potential and carrier concentration. Further, the photodetection parameters of the device, such as its linear dynamic range, rising time, and falling time, are evaluated to elucidate its spectral and transient characteristics. The device exhibits remarkably improved transient and spectral photodetection performances as compared to those of photodetectors based on atomically thin WS2 and two-dimensional materials. These results suggest that the proposed method is feasible for the manipulation of vertically standing WS2 layers that exhibit high in-plane carrier mobility and allow for high-performance broad-band photodetection and energy device applications.

Photocurrent Enhancement by a Rapid Thermal Treatment of Nanodisk-Shaped SnS Photocathodes.

Photocathodes made from the earth-abundant, ecofriendly mineral tin monosulfide (SnS) can be promising candidates for p/n-type photoelectrochemical cells because they meet the strict requirements of energy band edges for each individual photoelectrode. Herein we fabricated SnS-based cell that exhibited a prolonged photocurrent for 3 h at -0.3 V vs the reversible hydrogen electrode (RHE) in a 0.1 M HCl electrolyte. An enhancement of the cathodic photocurrent from 2 to 6 mA cm-2 is observed through a rapid thermal treatment. Mott-Schottky analysis of SnS samples revealed an anodic shift of 0.7 V in the flat band potential under light illumination. Incident photon-to-current conversion efficiency (IPCE) analysis indicates that an efficient charge transfer appropriate for solar hydrogen generation occurs at the -0.3 V vs RHE potential. This work shows that SnS is a promising material for photocathode in PEC cells and its performance can be enhanced via simple postannealing.

Enhanced broadband photoresponse of a self-powered photodetector based on vertically grown SnS layers via the pyro-phototronic effect.

Here, we demonstrate the broadband photoresponse from ultraviolet (365 nm) to near-infrared (850 nm) wavelengths from a photodetector based on vertically grown SnS layers. Particularly, the photoinduced current density of the device increased from 100 to 470 µA cm-2 with a wavelength of 760 nm and an intensity of 7 mW cm-2 by utilizing the pyro-phototronic potential. In addition, the photodetector demonstrated ultrafast response rates of ∼12 µs for the rise and ∼55 µs for the decay times over the studied range. Moreover, a good photoresponsivity of 13 mA W-1 and a high photodetectivity of 3 × 1014 Jones at a wavelength of 760 nm with an intensity of 7 mW cm-2 were measured, representing enhancements of 340% and 3960%, respectively, with the pyroelectric potential. This excellent broadband performance was attributed to the photon-induced pyroelectric effect in the vertically grown SnS layers, which also modulated the optoelectronic processes. This novel approach will open a new avenue to design a broadband ultrafast device for advanced optoelectronics.

Integrated spectral photocurrent density and reproducibility analyses of excitonic ZnO/NiO heterojunction.

In this data article, the excitonic ZnO/NiO heterojunction device (Patel et al., 2017) [1] was measured for the integrated photocurrent density and reproducibility. Photograph of the prepared devices of ZnO/NiO on the FTO/glass is presented. Integrated photocurrent density as a function of photon energy from the sunlight is presented. Quantum efficiency measurement system (McScienceK3100, Korea) compliance with International Measurement System was employed to measure ZnO/NIO devices. These data are shown for the 300-440 nm of segment of the sunlight (AM1.5G, http://rredc.nrel.gov/solar/spectra/am1.5/). Reproducibility measure of ZnO/NiO device was presented for nine devices with the estimated device performance parameters including the open circuit voltage, short circuit current density, fill factor and power conversion efficiency.

High-Speed, Self-Biased Broadband Photodetector-Based on a Solution-Processed Ag Nanowire/Si Schottky Junction.

In this work, we demonstrate the effectiveness of Ag nanowires (AgNWs) to design a high-speed broadband photodetector. A simple AgNW solution was spin-coated on a Si substrate to form a Schottky junction. The junction properties were investigated using current-voltage characteristics and Mott-Schottky analysis. The present device had a remarkably fast response speed, e.g., rising time τr = 784 ns and fall time τf = 92 µs, with good reproducibility over a wide range of switching frequencies (50 Hz-50 kHz). Such a high performance was attributed to the strong electric field created at the AgNW/Si interface without an external electric field, enabling the efficient separation of photogenerated electron-hole pairs. The present study will open a new avenue to design future optoelectronic devices and energy devices including solar cells.