Pyroelectric Research Articles

Enhanced performance of self-powered ultraviolet photodetectors coupled with the photovoltaic-pyroelectric effect based on ZnO/CuBO2 core-shell nanorod arrays

An innovative self-powered ultraviolet photodetector based on ZnO/CuBO 2 core-shell nanorod arrays was fabricated using cost-efficient and scalable preparation technologies, including a chemical hydrothermal method and an impregnation technique. The ZnO/CuBO 2 core-shell heterostructure exhibits significant diode behavior with a rectification ratio approaching 7016 at± 1 V because of the type-II band alignment formed at the heterojunction interface, acquiring a maximum responsivity of 165 mA /W1 with an external quantum efficiency of 55.3% (370 nm, 65 mW cm −2 ) and specific detectivity (4.13 ×10 12 cm Hz 1/2 W −1 ) under zero bias. Simultaneously, by applying an external bias to adjust the photovoltaic and pyroelectric effects and delving into the operating mechanisms, the photodetector based on the ZnO/CuBO 2 heterostructure achieves enhanced performance. The decay time has been shortened, and the responsivity has reached up to 38.82 A W −1 (apparent quantum efficiency ~ 13,010%) at − 2.5 V. Moreover, the effects of the power density on the photocurrent response and temperature induced by the photovoltaic-pyroelectric effect are discussed. This study reveals the potential of CuBO 2 (one of the Cu-delafossite families) as a hole transport layer in optoelectronic devices, broadens the application prospects of core-shell nanorod arrays based on the photovoltaic-pyroelectric effect, and provides a direction for modulating the performance of such devices. • CuBO 2 , as a p-type layer of copper delafossite, was firstly used to covered ZnO nanorods forming a core-shell structure. • The facile, convenient and low-cost processes were demonstrated to fabricate original self-powered ZnO NRs/CuBO 2 core-shell heterojunctions. • The performance of the photodetector has been enhanced by modulating photovoltaic and pyroelectric effects. • The curves of output current I pyr+pho , proportion of I pyr and temperature varying with the incident light power densities were fitted with the power-law I&T = AP α . • Significant excellent performance, e.g., R=165 mA W −1 @0 V, 38.82 A W −1 @-2.5 V (370 nm, 65 mW cm −2 ), D* λ =4.13×10 12 cm Hz 1/2 W −1 , RR=7016 at±1 V, was achieved for self-powered ultraviolet photodetectors with ZnO NRs/CuBO 2 core-shell sturcture.

Doping Sr and Introducing Oxygen Vacancies in Ba0.7Sr0.3TiO3‐X Synergistically Promote the Pyro‐Photo‐Electric Catalysis Performance

AbstractThe low utilization of light and the severe recombination of charge carriers have always restricted the development of photoelectric catalysis. In this work, the photoelectric catalytic performance is tuned by doping Sr in BaTiO3 pyroelectric material and simultaneously introducing oxygen vacancies to form double‐type defects, combined with pyroelectric polarization. Under the light and 20–50 °C cold‐heat cycle, the current density of Ba0.7Sr0.3TiO3‐X reaches the maximum of 0.92 mA ⋅ cm−2, which is higher than the current density of Ba0.7Sr0.3TiO3‐X under only light (0.69 mA ⋅ cm−2). Under light alone, the current density of Ba0.7Sr0.3TiO3‐X is higher than that of BaTiO3 (0.19 mA ⋅ cm−2) and Ba0.7Sr0.3TiO3 (0.44 mA ⋅ cm−2). This is because the incorporation of Sr can introduce the Fermi level, improve the utilization rate of solar energy, and improve the pyroelectric polarization effect with volume shrinkage, and promote the separation and transfer of carriers. Oxygen vacancies can be used as reactive centers for excited electrons to suppress the recombination of excited electron‐hole pairs. Furthermore, the generation of photogenerated and pyrogenerated carriers increases the overall carrier concentration. This provides ideas for the modification of traditional photoelectrodes for photoelectric catalysis water splitting.

Pyroelectric metamaterial millimeter-wave detector

We present experimental demonstration of a multi-functional metamaterial absorber, which operates as an efficient detector of millimeter wave radiation at room temperature. Intimate integration of a pyroelectric crystal directly within the metamaterial unit cell enables an efficient large area sensing element made up of repeating unit cells that are nearly ten times smaller than the operational wavelength. An un-amplified intrinsic responsivity of 3.90 V/W is demonstrated at 91.5 GHz, which is close to the peak of the spectral absorption at 97.8 GHz. Numerical full-wave electromagnetic simulations match well to experiments and clarify the underlying absorption mechanism, while thermal simulations permit optimization of the responsivity. The demonstrated results show that the monolithic pyroelectric metamaterial geometry well functions as a detector and represents an ideal device platform for realization of novel and compact room temperature millimeter wave sensing and imaging components.

Design of Self‐Powered Sensors with Excellent Thermal and UV–Light Detections by 0.94(Bi0.5Na0.5)TiO3‐0.06Ba(Zr0.25Ti0.75)O3 Nanoparticles

AbstractFerroelectric materials provide a new pathway to convert thermal energy into electricity based on the pyroelectric effect. How to modulate the pyroelectric property of ferroelectric materials through UV–light is still an urgent problem that needs to be solved. Here, a self‐powered sensor is demonstrated based on 0.94(Bi0.5Na0.5)TiO3‐0.06Ba(Zr0.25Ti0.75)O3 nanoparticles, exhibiting high output electric performance under temperature variation and UV–light illumination conditions. Compared with a purely pyroelectric system, the corresponding current peaks of “UV–light + heating” and “UV–light + cooling” states are 88.6% higher and 37.3% smaller in the coupled system. The fabricated pyroelectric system shows excellent performance with detection sensitivities of 0.9 (heating) and 1.48 nA K−1 (cooling) with 0.7 × 10−3 and 0.2 × 10−3 nA lux−1 illuminated by 395 nm UV–light as a temperature sensor. Furthermore, a self‐powered sensor that is suitable for detecting both UV–light and temperature variations by recording the output current signals are demonstrated, which provides a basis for the development of the next generation of UV–light‐modulated ferroelectric devices.

Inducing photocarrier separation via 3D porous faveolate cross-linked carbon to enhance photothermal/pyroelectric property

The CdS/Bi2S3 supported three-dimensional (3D) porous faveolate carbon structure (CdS/Bi2S3@C) composite photocatalyst was constructed. Bi2S3 nanoparticles are regarded as photothermal agents and pyroelectric materials to absorb near infrared light (NIR) and convert it into heat. 3D porous faveolate of carbon acts as incubator to reduce heat loss and optimize photothermal effects. There is a greater fluctuating temperature difference (ΔΤ) between photothermal effect of Bi2S3 and cold photocatalytic system. This enhances the pyroelectric effect that Bi2S3 undergoes spontaneous polarization and releases the surface charge. Therefore, the separation of electrons and holes in the CdS photocatalyst can be induced. The COMSOL simulation results show that, the higher pyroelectric potential producted by larger ΔΤ is more favorable to the photocatalytic process. The hydrogen evolution rate of CdS/Bi2S3@C photocatalyst can reach 5.88 ​mmol·g−1·h−1 with excellent cycle stability.

Electrocaloric studies of bulk materials and multilayer structures by dynamic infrared radiometry

A new experimental approach to the complex study of electrocaloric, pyroelectric, and thermal effects associated with the bulk and local electrical conductivity of ferroelectrics and related materials is proposed. The key to this approach is the analysis of the dynamics of the sample temperature response to an arbitrary external action, including long-term electrical impacts. The metrological justification of the experimental technique is based on direct non-contact high-speed monitoring of the sample temperature using an IR photodiode sensor designed by Ioffe Institute. Its efficiency is confirmed by numerous experimental data on electrocaloric properties of ferroelectrics, relaxors, and relaxors-based multilayer structures.

Construction of NaNbO3/CdS nanorods composites with pyroelectric effect for enhanced pyrocatalytic and antibacterial activity under room-temperature cold-hot cycles

In the present study, NaNbO3-CdS nanorods composites with pyroelectric effect were used to degrade RhB solution and sterilize Salmonella under room-temperature cold-hot cycles. The pyrocatalytic decomposition rate of NaNbO3-CdS reached 90 % under 45 cold-hot (25–55 °C) cycles while the antibacterial rate of NaNbO3-CdS also achieved 90 % under 45 cold-hot (17–37 °C) cycles. Compared with the pyrocatalytic effect of single NaNbO3, with the hole’s radicals and superoxide radicals as the main active species, the pyrocatalytic effect of the NaNbO3-CdS was significantly enhanced. It is mainly attributed to its surface electrons being captured by CdS, thereby reducing the recombination probability of electron pairs. After four repeated experiments, the high pyrocatalytic activity still maintained, which indicated that the property of NaNbO3-CdS composites was stable. The composite nanocatalyst has potential in the degradation of dye pollution and sterilization by temperature difference.

High-performing UV photodetectors by thermal-coupling transparent photovoltaics

Understanding of light-driven electric power (photovoltaics) and thermally–induced electric (pyroelectric) effect is crucial for the next-generation of optoelectronics, emphasizing sustainability and portability with improved performance. Herein, we report the high-performing thermal-coupling transparent photovoltaics for ultrafast photodetection. Optically transparent photovoltaic device has p–n heterojunction, with n-ZnO and two different p-type metal oxides (Cu2O or NiO). The ZnO based photodetector is highly transparent with average visible transmittance of 51%. Importantly, significant enhancement of device sensitivity toward ultraviolet (UV) light (λ = 365 nm) is obtained via tuning the pyroelectric effect of ZnO. The pyro-current is originated from polarization charges due to thermal variation, thus the control of heat flow in ZnO is the origin to enhance pyro-current. The lower thermal conductivity of Cu2O (4.5 W m−1 K−1) is more effective rather than the case of NiO to shape the well-confined heat in ZnO thermal reservoir, resulting in the significantly enhanced pyro-current (176.3%). The transparent ZnO/Cu2O photodetector exhibits the extremely-high responsivity of 0.98 A W−1 and detectivity of 1.62 × 1013 Jones, with μs response speed at zero bias condition due to the photovoltaic operation. This will bring the self-support transparent electronics for versatile see-through platforms without bulky power system. One day people will get information quickly and wireless without loss of vision.

Application of Temperature Compensation Combined with Neural Network in Infrared Gas Sensor

Due to the state of the gas to be measured, the detection mechanism of the pyroelectric detector and the temperature drift of the peripheral circuit components and the detection of the ambient temperature will interfere with the measurement accuracy of the nondispersive infrared gas sensor from many aspects. This paper proposes a temperature compensation method based on the BP neural network. The compensation function of the gas sensor is realized by programming the various functional parameters in the neural network through the program provided in the Matlab neural network toolbox. Experimental simulation results show that the proposed method effectively reduces the influence of external temperature on the gas sensor output and improves its accuracy and stability.

Performance and mechanism of hydrogen evolution from room-temperature thermal catalytic water splitting by α-phase Si3N4

Because α-Si3N4 has a noncentrosymmetrical crystal pattern capable of self-polarizing point groups, it is theoretically pyroelectric. When the ambient temperature changes, the surface of a pyroelectric semiconductor will produce abundant compensationary charges q+ and q-, which theoretically can be used into hydrogen evolution from water splitting. In this study, the piezoelectric and pyroelectric performances of α- Si3N4were validated by piezoelectric force microscopy and potassium permanganate reduction experiments. Based on the pyroelectric performance of α- Si3N4 and with methanol as the sacrificial agent, hot–cold cycles were conducted from room temperature (27 °C) to 60 °C. Per gram of catalysts can produce 12.32 μmol/g hydrogen after 20 cycles, and the hydrogen yields after repeated experiments did not significantly decrease, proving that Si3N4 has high stability and that the pyroelectric effect is highly potential for hydrogen production from water splitting.

Chemical Nature of Heterogeneous Electrofreezing of Supercooled Water Revealed on Polar (Pyroelectric) Surfaces.

ConspectusThe ability to control the icing temperature of supercooled water (SCW) is of supreme importance in subfields of pure and applied sciences. The ice freezing of SCW can be influenced heterogeneously by electric effects, a process known as electrofreezing. This effect was first discovered during the 19th century; however, its mechanism is still under debate. In this Account we demonstrate, by capitalizing on the properties of polar crystals, that heterogeneous electrofreezing of SCW is a chemical process influenced by an electric field and specific ions. Polar crystals possess a net dipole moment. In addition, they are pyroelectric, displaying short-lived surface charges at their hemihedral faces at the two poles of the crystals as a result of temperature changes. Accordingly, during cooling or heating, an electric field is created, which is negated by the attraction of compensating charges from the environment. This process had an impact in the following experiments. The icing temperatures of SCW within crevices of polar crystals are higher in comparison to icing temperatures within crevices of nonpolar analogs. The role played by the electric effect was extricated from other effects by the performance of icing experiments on the surfaces of pyroelectric quasi-amorphous SrTiO3. During those studies it was found that on positively charged surfaces the icing temperature of SCW is elevated, whereas on negatively charged surfaces it is reduced. Following investigations discovered that the icing temperature of SCW is impacted by an ionic current created within a hydrated layer on top of hydrophilic faces residing parallel to the polar axes of the crystals. In the absence of such current on analogous hydrophobic surfaces, the pyroelectric effect does not influence the icing temperature of SCW. Those results implied that electrofreezing of SCW is a process influenced by specific compensating ions attracted by the pyroelectric field from the aqueous solution. When freezing experiments are performed in an open atmosphere, bicarbonate and hydronium ions, created by the dissolution of atmospheric CO2 in water, influence the icing temperature. The bicarbonate ions, when attracted by positively charged pyroelectric surfaces, elevate the icing temperature, whereas their counterparts, hydronium ions, when attracted by the negatively charged surfaces reduce the icing temperature. Molecular dynamic simulations suggested that bicarbonate ions, concentrated within the near positively charged interfacial layer, self-assemble with water molecules to create stabilized slightly distorted “ice-like” hexagonal assemblies which mimic the hexagons of the crystals of ice. This occurs by replacing, within those ice-like hexagons, two hydrogen bonds of water by C–O bonds of the HCO3– ion. On the basis of these simulations, it was predicted and experimentally confirmed that other trigonal planar ions such as NO3–, guanidinium+, and the quasi-hexagonal biguanidinium+ ion elevate the icing temperature. These ions were coined as “ice makers”. Other ions including hydronium, Cl–, and SO4–2 interfere with the formation of ice-like assemblies and operate as “ice breakers”. The higher icing temperatures induced within the crevices of the hydrophobic polar crystals in comparison to the nonpolar analogs can be attributed to the proton ordering of the water molecules. In contrast, the icing temperatures on related hydrophilic surfaces are influenced both by compensating charges and by proton ordering.

Nonmetallic surface plasmon resonance coupling with pyroelectric effect for enhanced near-infrared-driven CO2 reduction

Plasmonic semiconductors with both features of metals and semiconductors are expected materials for solar light harvesting. Here, plasmonic semiconductor heterostructures were constructed by coupling pyroelectric black phosphorus (BP) and plasmonic tungsten oxides (WO) as photocatalyst for CO2 reduction. Intriguingly, under visible and near-infrared (NIR) light irradiation, the plasmonic BP/WO heterostructures with optimal composition exhibit high-selective 26.1 μmol g-1h−1 CO generation (98 %), which is 7- and 17-fold higher than those of plasmonic WO and pyroelectric BP, respectively. The interface bonds (P-O-W) were detected by FTIR spectra and demonstrated by density functional theory (DFT) calculations as dominant channels for electron transfer from BP to WO. Plasmonic thermal effect of WO can increase the local temperature to 86 °C under visible and NIR light irradiation, triggering pyroelectric effect of BP and generating pyroelectric carriers, which enhance the electron transfer from BP to WO. Therefore, continuous electron injection from pyroelectric BP to WO enhances surface plasmon resonance for high-selective CO2 reduction. This work provides clear proofs to demonstrate that constructing pyroelectric effect on plasmonic heterostructures is one useful strategy to promote NIR-harvesting for artificial photosynthesis.

Peculiarities of the electrocaloric effect in relaxors

A comprehensive study and detailed analysis of pyroelectric and electrocaloric effects in relaxor ferroelectrics based on lead magnesium niobate as a promising object for such investigations have been carried out. It was found that even at the maximum values of pyroelectric coefficients the electrocaloric response inextricably linked with the pyroelectric effect does not exceed 1 °C in the temperature range from 10 to 60 °C under DC electric field up to 60 kV/cm. These conditions are the most demanded for the operation of electrocaloric cooling devices. Vision for the future as to increasing the efficiency of the main elements for such devices is discussed.

Femto Seconds Laser Based Efficient THz Generation from Different Temperature Annealed CdTe Thin Films and Effects of Carrier Concentration and Phase Transition on Efficiency of Generation

The paper reports the thermal evaporation based growth process of CdTe thin films on glass substrates. These films were annealed between room temperature to 200, 300 and 400 oC, respectively. The XRD characterization of these films revealed the change in crystalline phase from cubic to triclinic above 200 oC. Finally, these films were subjected to 800 nm wavelength of 35fs pulsed obtained from Ti: sapphire amplifier at 1kHz repetition rate. The incident power of the laser was focused and tuned between 150-350 mW range and generated THz signals were recorded using calibrated Pyroelectric detector at 22.5 Hz frequency. The highest power of the THz signal was 80nW for 200 oC annealed film with respect to incident power of 300mW. The highest efficiency of THz signal was of the order of 3.11E-5%. We have also explained the effect of carrier concentration and phase transition with respect to different annealed temperature for efficient generation of THz signal.

Measurement of stress distribution at the nanoscale: Towards stress nanotomography

We develop an experimental method for the in-situ stress measurement at the nanoscale. It provides a stress distribution in a contact zone between a probe and a pyroelectric crystal, based on the piezoelectric effect. We elaborate a theory of the method and demonstrate that the continuum theory of elasticity and piezoelectricity remains valid at the nanoscale. We show that the stress in the bulk of the contacting bodies may be also reconstructed, thus paving a way to 3D stress nanotomography.

Bioinspired materials: Physical properties governed by biological refolding

Peptide and protein biomolecules folded into two fundamentally different conformations, either α-helical or β-sheet, carry out dissimilar biological functions. In living organisms, an α-helical secondary structure is adopted by different types of proteins such as myoglobin, keratin, collagen, and more. They can be found in diverse biological tissues of muscle, bone, cartilage, etc.. Biological functions of β-sheet peptide/protein structures are different and associated with a wide range of human mental amyloid diseases such as Alzheimer and Parkinson. The fundamental basis of these diseases is misfolding or refolding of natively soluble α-helical amyloid proteins into solid-state β-sheet fibrillary structures. Bioinspired chemically synthesized biomolecules mimic their biological counterparts. Although these artificial and biological peptides/proteins molecules are completely dissimilar in origin and environment, they demonstrate the common properties of folding and refolding into identical secondary architectures. In this review, we show that these two structural conformations, native (helix-like) and β-sheet, exhibit exclusive and different sets of fold-sensitive physical properties that are surprisingly similar in both biological and bioinspired materials. A native (helix-like) self-assembled fold having asymmetric structure demonstrates ferroelectric-like pyroelectric, piezoelectric, nonlinear optical, and electro-optical effects. β-sheet peptide/protein structures acquire unique visible fluorescence (FL) and reveal a new property of lossless FL photonic transport followed by a long-range FL waveguiding in amyloidogenic fibers. An applied thermally mediated refolding native-to-β-sheet allows us to observe adoption, disappearance, and switching of the revealed physical properties in detail in each fold and study dynamics of all critical stages of refolding from the metastable (native) helix-like conformation via intermediate disordered state to stable β-sheet fibrillary ordering. In the intermediate state, the appearance of the visible FL provides imaging, monitoring, and direct observation of the early stages of seeding and nucleation of β-sheet fibrils. The diverse fold-sensitive physical properties found, give a new insight into biological refolding processes and pave the way for the development of advanced physical methods of fold recognition, bioimaging, light theranostics at nanoscale, and peptide/protein nanophotonics from new visible FL bionanodots to bioinspired multifunctional peptide photonic chips.

Self-powered, broadband, and polarization-sensitive pyroelectric-photoelectric photodetector based on silicon-water heterojunction

The coupling of pyroelectric and photoelectric effects is a new method to enhance transient response while maintaining steady-state response in photodetectors. Such photodetectors have recently attracted a great attention due to a wide range of potential applications including artificial electronic eyes, neuromorphic computing, color sensors, and optical communications. Here, we report a photodetector based on the pyroelectricity and photoelectricity effect in a silicon-water heterojunction for the first time. Facilitated by the polarity of water on the Si surface, this heterostructure serves as a pyroelectric-based photodetector with a responsivity as high as 754 mA/W and specific detectivity as high as 1.33 × 1013 Jones under a light wavelength of 400 nm at zero bias. Also, the formation of a built-in electric field at the silicon-water interface results in a photoelectric-based photodetector with a responsivity as high as 12.3 A/W and an ultrahigh detectivity of 2.18 × 1014 Jones at −2 V bias under steady-state conditions. Moreover, due to the polarization-sensitive reflection of light on the water surface, this structure is also polarization-sensitive. These photodetectors are suitable for liquid-compatible applications that require broadband detection, high responsivity, and polarization-sensitivity.

A simple method for estimating the potential of the pyroelectric crystal surface

The potential of the pyroelectric crystal surface has been estimated using experimental data. The temperature of the pyroelectric crystal, the electron current from the crystal surface to the target, and the X-ray spectrum were simultaneously measured. The potential calculated from the temperature and the electron current was compared with the experimental endpoint energy of the X-ray spectrum. The calculated potential reasonably agreed with the experimental endpoint energy.

Pyroelectric detector-based method for low uncertainty spectral irradiance and radiance responsivity calibrations in the infrared using tunable lasers.

The standard uncertainty of detector-based radiance and irradiance responsivity calibrations in the short-wave infrared (SWIR) traditionally has been limited to around 1% or higher by the poor spatial uniformity of detectors used to transfer the scale from radiant power. Pyroelectric detectors offer a solution that avoids the spatial uniformity uncertainty but also introduces additional complications due to alternating current (AC) measurement techniques. Herein, a new, to the best of our knowledge, method for low uncertainty irradiance responsivity calibrations in the SWIR is presented. An absolute spectral irradiance responsivity scale was placed on two pyroelectric detectors (PED) at wavelengths λ from 500 to 3400 nm. The total combined uncertainty (k=1) was ≈0.28% (>1000nm), 0.44% (900 nm), and 0.36% (≈950nm and <900nm) for PED #1 and 0.34% (>1000nm), 0.48% (900 nm), and 0.42% (≈950nm and <900nm) for PED #2. This was done by utilizing a demodulation technique to digitally analyze the time-dependent AC waveforms, which obviates the use of lock-in amplifiers and avoids associated additional uncertainty components.

Observation of X-rays during heating a pyroelectric crystal by an infrared laser

A pyroelectric X-ray source is proposed, in which a lithium tantalate crystal is heated by an infrared laser with a wavelength of 10.6 μm. X-ray spectra measured during irradiation of the crystal with infrared radiation and during natural cooling of the crystal include characteristic X-ray radiation of atoms contained in the structural parts of the source, as well as bremsstrahlung of electrons with energies above 50 keV. An 8 mm sodium chloride window was used to inject 64 W infrared radiation into a vacuum chamber with the pyroelectric crystal installed.