Maximum Rectification Ratio Research Articles

Optically Mediated Hydrogel-Based Ionic Diode.

Ionic diodes with environmentally modulated ion-rectifying characteristics have attracted much attention and show great promise in the construction of smart devices with environmental adaptability. One immediate challenge is to integrate stimuli responsiveness and ion rectification into one single ionic diode, which requires a close cooperation of chemical principles and device technologies. Herein, an ionic diode based on a photoresponsive hydrogel with optically mediated ion-rectifying performances is introduced. Relying on the photoresponsive concentration of proton in the hydrogel, the ionic current rectification can be prominently enhanced upon ultraviolet (UV) irradiation. A maximum ionic current rectification ratio of the optically mediated ionic diode about 4× 105 is achieved. Furthermore, the hydrogel-based diode can serve as an AND logic gate operated by UV light and voltage bias as two independent inputs. As a proof of concept, to use the optically mediated diode is achieved to modulate the feedback of a robot with logic behaviors. This work provides a novel and valuable strategy for designing functional hydrogel-based devices with the integration of stimuli-responsiveness and logic signal processing through chemical approaches.

High rectification effects of heterojunctions based on C3N4 nanoribbons

Two heterojunctions based on zigzag graphitic carbon nitride nanoribbons (ZCNNRs), namely, BnAn and CnAn, are considered and their electronic transport properties are studied using the nonequilibrium Green's function (NEGF) in combination with the density functional theory (DFT). The BnAn is formed by the joining of bare and partially hydrogenated ZCNNRs. The CnAn is created by the attachment of bare and fully hydrogenated ZCNNRs which leads to a Schottky barrier. The results show that current–voltage characteristics (I–V) can be significantly tuned by the length variation of heterojunctions. Furthermore, it is found that both heterojunctions have a remarkable nonlinear behavior in the whole bias range. The B4A4, B3A4, and B4A3 have forward rectifier performance whereas B2A2, B3A3, C2A2, C3A3, C4A4, C3A4, C4A3, C5A3, and C6A3 show the reverse rectification behavior. In the case of BnAn, the maximum rectification ratio (RR) of B4A4 is boosted up to 3.97 × 107 at 0.4 V. Additionally, for CnAn, the maximum RR of C4A3 can reach 1.37 × 105 at 1.0 V. Our investigation reveals that the BnAn heterojunction has negative differential resistance (NDR) under positive bias.The peculiar transport behaviors of B4A4 and C4A3 are explained due to the energy level shifts of electrodes with applied bias voltage and great alterations in the transmission spectrum. Furthermore, the Molecular projected self-consistent Hamiltonian (MPSH) and projected local density of states (PLDOS) are analyzed for these devices. The findings of this work reveal unique opportunities to design the ZCNNRs nanoelectronic devices.

Teflon AF–Coated Nanotextured Aluminum Surfaces for Jumping Droplet Thermal Rectification

AbstractJumping droplet thermal diodes (JDTDs) are promising candidates to achieve thermal rectification for next‐generation thermal control. However, most prior demonstrations of JDTDs have relied on monolayer‐coated copper‐based superhydrophobic (SHPB) surfaces, while lower‐cost aluminum JDTDs with more durable thin polymeric coatings have not been explored. In this work, a JDTD is constructed that employs SHPB aluminum surfaces coated with protective thin films of Teflon AF (amorphous fluoropolymer) 1601. Measurements for different heating orientations, gap heights (H), and fill ratios (ϕ) show that a maximum thermal rectification ratio of 7 can be achieved for H = 2.4 mm and ϕ = 10%. A thermal circuit is demonstrated that uses the JDTD to rectify time‐periodic temperature profiles, achieving thermal circuit effectiveness values up to 30% of the ideal‐diode limit. Coupon‐level durability tests and device‐level cycling show that dip coated Teflon AF enables stable operation of Al JDTDs over >20 cycles, improving on the performance of a monolayer‐coated surface that fails after 5 cycles. The findings of this work signify that Teflon AF coated Al SHPB surfaces can be used for thermal rectification and motivate future research into Al JDTDs for advanced thermal management applications.

Self-Powered Photodetector Based on Ag/CH3NH3PbI3/C Asymmetric Dual-Terminal Device.

CH3NH3PbI3 is capable of exhibiting a superior photoresponse to visible light, but its self-powered devices are typically formed through p-n junctions. In this study, we fabricated a Ag/CH3NH3PbI3/C dual-terminal asymmetric electrode device using a single CH3NH3PbI3 perovskite micro/nanowire, enabling both the photoresponse and self-powered characteristics of CH3NH3PbI3 to visible light. Compared with traditional p-n junction devices, this simple device demonstrates enhanced interface photovoltaic effects by optimizing the combination of the Ag electrode with CH3NH3PbI3, resulting in superior self-powered characteristics. Under low bias voltage, the device achieves a significant on/off ratio of 103, with superior sensitivity and responsivity as well as a maximum rectification ratio of about 12. The photogenerated voltage and current reach approximately 0.8 V and 2 nA, respectively. This simple, compact, and self-powered asymmetric device exhibits great potential for applications in self-powered optoelectronics and wearable devices. This research provides a promising approach for recognizing and utilizing surface state effects in single nanoscale structures.

High-rectification near-field radiative thermal diode using Weyl semimetals

Thermal diodes, which allow heat transfer in a preferential direction while being blocked in a reverse direction, have numerous applications in thermal management, information processing, energy harvesting, etc. Typical materials of thermal diodes in previous works include phase-change and magneto-optical materials. However, such thermal diodes depend highly on specific working temperatures or external magnetic fields. In this work, we propose a near-field radiative thermal diode (NFRTD) based on two Weyl semimetal (WSM) nanoparticles (NPs) mediated by a WSM planar substrate, which works without an external magnetic field and with flexible temperatures. Numerical results show that the maximum rectification ratio of NFRTD can be up to 2673 when the emitter is 200 K and receiver is 180 K, which exceeds the maximum value reported in some previous works by more than 10 times. The underlying physical mechanism is the strong coupling of the localized plasmon modes in the NPs and nonreciprocal surface plasmon polaritons in the substrate. In addition, we calculate the distribution of the Green's function and reflection coefficient to investigate nonreciprocal energy transfer in NFRTDs. Finally, we discuss the effects of momentum separation on the rectification performance of the NFRTD. This work demonstrates the great potential of WSMs in thermal rectification and paves a path for designing high-performance NFRTDs.

Near-field thermal diode based on 2D gratings

This paper proposes a near-field thermal diode (NFTD) based on VO2 and cBN 2D gratings to improve the rectification ratio. Different from previous studies, this paper is the first to verify the positive effect of 2D gratings on NFTD. The exact calculations are based on rigorous coupled wave analysis (RCWA). After optimization, the rectification ratio of the 2D grating-based NFTD reaches the maximum R = 29.5 at filling factor f = 0.04 and gap distance d = 100 nm, which is nearly four times larger than the optimal result of the plain-based one. The reason for the improvement of rectification ratio is that the reverse spectral heat flux is weakened by more than an order of magnitude in nearly the whole spectrum, while the forward spectral heat flux is influenced little in the hyperbolic regions. Besides, the lattice period P = 100 nm and grating height h = 1 μm are feasible solutions for symmetric configurations. The validity of effective medium theory (EMT) for calculating 2D grating-based NFTD is also investigated. The EMT is consistent with RCWA in predicting the optimal filling factor and grating height at d = 100 nm, but is invalid in predicting the optimal gap distance and the maximum rectification ratio. The longitudinal asymmetric configuration is further proposed by changing the structural parameters. When the size ratios of cBN grating and VO2 grating are selected as 0.6 and 0.1, respectively, the rectification ratio is better than the symmetric configuration due to the broadening of the hyperbolic region during forward bias. After optimizing grating height, the rectification ratio further reaches 54. Our study deepens the understanding of the rectification mechanism of 2D grating-based thermal diodes and paves the way for potential applications of thermal diodes.

TiO2 nanoarrays/Au nanoparticles/PProDOT-Py hybrid heterojunction UV photodetector

In this paper, a novel D-A-D type conducting polymer (PProDOT-Py) with pyridine as acceptor unit and 3,4-propanedioxythiophene as donor unit was prepared for heterojunction ultraviolet (UV) photodetector based on TiO 2 NRs/Au NPs. The effect of PProDOT-Py on the UV photodetection properties was deeply discussed. The results showed that PProDOT-Py was unevenly dispersed on TiO 2 NRs in the form of cross-linked network, and there were coordination bonds between TiO 2 NRs and PProDOT-Py. The matching of the energy levels between PProDOT-Py and TiO 2 was helpful for formation of heterojunction hybrid.The maximum rectification ratio of TiO 2 NRs/Au NPs/PProDOT-Py was 54 under bias voltage of −2 to 2 V, implying that the p-n heterojunction in the internal structure of TiO 2 NRs/Au NPs/PProDOT-Py. The Fermi level of TiO 2 NRs was changed by the presence of PProDOT-Py, which generated the p-n heterojunction for producing strong inherent electric field. In addition, D* and I photo /I dark of UV photodetector based on TiO 2 NRs/Au NPs/PProDOT-Py were 1.067 × 10 13 Jones and 17857.14 (2 V), respectively. Under the condition of self-power supply, the device has an ultrafast response time of 0.06 s. • ProDOT-Py was synthesized for the first time. • TiO 2 NRs/Au NPs/PProDOT-Py composite shows superior UV detection performance under 2V bias voltage. • PProDOT-Py can form coordination bond with TiO 2 and Au NPs can strongly interact with PProDOT-Py.

Bioinspired Dual-Driven Binary Heterogeneous Nanofluidic Ionic Diodes.

Recently, bioinspired 2D material-based nanofluidic systems with unique properties and advantages have been receiving considerable research interest and getting rapid development. However, it remains a huge challenge to integrate adaptive responsiveness to external stimuli and asymmetric ion transport characteristics into the 2D nanofluidic systems. Herein, we report a dual-driven switchable asymmetric ionic transport phenomenon through a graphene oxide-based heterogeneous 2D nanofluidic membrane. Taking advantage of the formation of a charge heterojunction induced by the variation of pH or UV irradiation, a maximum ionic current rectification (ICR) ratio of ca. 56 for pH or 140 for light was achieved. Such smart nanofluidic devices with pH and light dual-responsiveness and asymmetric ion transport behaviors provide a universal strategy for potential applications in chemical sensing, water treatment, and energy conversion and establish a promising platform for exploring advanced quantum ionics biodevices with ultrafast signal transmission, nanochannel-structured bioreactors with high efficiency, etc.

Synthesis of a Selectively Nb-Doped WS2-MoS2 Lateral Heterostructure for a High-Detectivity PN Photodiode.

In this study, selective Nb doping (P-type) at the WS2 layer in a WS2-MoS2 lateral heterostructure via a chemical vapor deposition (CVD) method using a solution-phase precursor containing W, Mo, and Nb atoms is proposed. The different chemical activity reactivity (MoO3 > WO3 > Nb2O5) enable the separation of the growth temperature of intrinsic MoS2 to 700 °C (first grown inner layer) and Nb-doped WS2 to 800 °C (second grown outer layer). By controlling the Nb/(W+Nb) molar ratio in the solution precursor, the hole carrier density in the p-type WS2 layer is selectively controlled from approximately 1.87 × 107/cm2 at 1.5 at.% Nb to approximately 1.16 × 1013/cm2 at 8.1 at.% Nb, while the electron carrier density in n-type MoS2 shows negligible change with variation of the Nb molar ratio. As a result, the electrical behavior of the WS2-MoS2 heterostructure transforms from the N-N junction (0 at.% Nb) to the P-N junction (4.5 at.% Nb) and the P-N tunnel junction (8.1 at.% Nb). The band-to-band tunneling at the P-N tunnel junction (8.1 at.% Nb) is eliminated by applying negative gate bias, resulting in a maximum rectification ratio (105) and a minimum channel resistance (108 Ω). With this optimized photodiode (8.1 at.% Nb at Vg = -30 V), an Iphoto/Idark ratio of 6000 and a detectivity of 1.1 × 1014 Jones are achieved, which are approximately 20 and 3 times higher, respectively, than the previously reported highest values for CVD-grown transition-metal dichalcogenide P-N junctions.

Electronic transport in biphenylene network monolayer: Proposals for 2D multifunctional carbon-based nanodevices

Very recently, the experimental synthesis of biphenylene network (BPN) monolayer has achieve a great progress (Matetskiy et al., 2021). However, a systematic study of the potential devices based on the BPN monolayer is still lacking up to date. In this paper, several conceptual BPN-based nanodevices are proposed and their electronic transport properties are revealed by using the density functional theory combined with non-equilibrium Green’s function method. First, the pristine BPN-based devices exhibit obvious electronic transport anisotropy along the zigzag and armchair directions. Moreover, a significant negative differential resistance (NDR) effect along the armchair direction is observed as well. Second, the gas sensitivities of the BPN-based gas sensor to NO and NO2 along the armchair direction are as high as 1.63 and 2.75, respectively. Finally, the BPN monolayer undergoes a metal–semiconductor transition in the case of N13 or N14 doping strategy. Therefore, Schottky junction device formed by the pristine and N14 doped BPN monolayer is constructed and its maximum rectification ratio reaches ∼104 at low bias voltage. These results demonstrate that the BPN monolayer is a multifunctional material and may find various potential applications in electronic anisotropy, NDR, gas sensor, and even Schottky junction devices.

Heat-pipe-based tunable multimode horizontal thermal rectifier

A heat-pipe-based multimode thermal rectifier, easily scalable for advanced thermal energy management in industrial applications (e.g., waste heat recovery, solar energy application and building energy management), is proposed for horizontal heat transport. The thermal rectifier is composed of a copper tube loop having a superhydrophilic section and a superhydrophobic section. The thermal rectification effect is achieved by the differences of the superhydrophilic and superhydrophobic sections in surface evaporation/condensation and wicking characteristics, when they are exposed to heating or cooling. Meanwhile, a valve is incorporated in the vapor channel to control the switch status of the hot vapor flow. Experiments with such a thermal rectifier showed that a maximum thermal rectification ratio of 4.18 could be reached at the heat flux of 3222 W/m2, whereas a higher rectification ratio (up to 5.78) could even be achieved when forward and reversed heat transfer are at different heating temperatures in real applications. Besides, the forward thermal conductivity could reach 623 W/(m⋅K) for efficient waste heat harvest. In addition, the thermal rectification ratio, as well as the heating mode, can be tuned by the status of the valve in the tube loop to satisfy the complex requirement in practical applications.

Nanoporous Kevlar Aerogel Confined Phase Change Fluids Enable Super‐Flexible Thermal Diodes

AbstractAerogels have demonstrated tremendous potentials for various applications, including thermal insulation, environmental protection, and separation. However, aerogels as porous frameworks to host functional liquids (such as phase change fluids, PCFs) is a more promising application, attributing to their large specific surface area, high porosity, and strong capillary force. Herein, the original aramid nanofiber (OANF, i.e., Kevlar) aerogel film and the densified ANF (DANF) aerogel film are fabricated and thereafter applied to confine phase change fluids, poly (N‐isopropylacrylamide) (PNIPAM) solution and molten eicosane (C20), respectively, to make super‐flexible OANF‐PNIPAM and DANF‐C20 films accordingly. These two films exhibit reversely temperature‐dependent thermal conductivity with close phase change temperature to each other. Therefore, flexible thermal diodes operating with terminals of OANF‐PNIPAM film and DANF‐C20 film are proposed and fabricated, showing excellent flexibility (420 µm in curvature radius) and robustness (≥7.2 MPa in tensile strength) as well as the maximum thermal rectification ratio of 2.0. This work paves a way for expanding the applications of Kevlar aerogel confined phase change fluids, as well as provides a promising strategy for designing more practical thermal diodes and thermal devices.

Thermal diode based on a multilayer structure of phase change materials

Thermal diodes are devices that allow heat to flow preferentially in one direction. This unique thermal management capability has attracted attention in various applications, like electronics, sensors, energy conversion or space applications, among others. Despite their interest, the development of efficient thermal diodes remains still a challenge. In this paper, we report a scalable and adjustable thermal diode based on a multilayer structure that consists of a combination of phase change and phase invariant materials. We applied a parametric sweep in order to find the optimum conditions to maximize the thermal rectification ratio. Our simulations predicted a maximum thermal rectification ratio of ~20%. To evaluate the impact of these devices in real applications, we theoretically analysed the performance of a magnetocaloric refrigerating device that integrates this thermal diode. The results showed a 0.18 K temperature span between the heat source and the heat sink at an operating frequency of 25 Hz.

Large Thermal Rectification in a Solid-State Thermal Diode Constructed of Iron-Doped Nickel Sulfide and Alumina

Thermal diodes, which allow heat flow in one direction but prohibit it in the reverse direction, are fundamental for thermal manipulation. Here, we report the construction of a thermal diode consisting of ${\mathrm{Ni}}_{0.85}{\mathrm{Fe}}_{0.15}\mathrm{S}$ (bonded with 10 wt % silver) and alumina. A high rectification factor \ensuremath{\gamma} of 1.51 is achieved with a relatively small temperature bias of 97 K near room temperature, indicating great potential applications in the field of nonlinear thermal control. The excellent rectification effect is attributed to the high contrast change in thermal conductivity of ${\mathrm{Ni}}_{0.85}{\mathrm{Fe}}_{0.15}\mathrm{S}$. In addition, we demonstrate that the maximum thermal rectification ratio is strongly dependent on the cold-terminal temperature of the thermal diode, the length ratio between the two segments, and the steepness of the first-order phase transition of ${\mathrm{Ni}}_{0.85}{\mathrm{Fe}}_{0.15}\mathrm{S}$.

A passive Stokes flow rectifier for Newtonian fluids

Non-linear effects of the Navier–Stokes equations disappear under the Stokes regime of Newtonian fluid flows disallowing a flow rectification behavior. Here we show that passive flow rectification of Newtonian fluids is obtainable under the Stokes regime of both compressible and incompressible flows by introducing nonlinearity into the otherwise linear Stokes equations. Asymmetric flow resistances arise in shallow nozzle/diffuser microchannels with deformable ceiling, in which the fluid flow is governed by a non-linear coupled fluid–solid mechanics equation. The proposed model captures the unequal deflection profile of the deformable ceiling depending on the flow direction under the identical applied pressure, permitting a larger flow rate in the nozzle configuration. Ultra-low aspect ratio microchannels sealed by a flexible membrane have been fabricated to demonstrate passive flow rectification for low-Reynolds-number flows (0.001 < Re < 10) of common Newtonian fluids such as water, methanol, and isopropyl alcohol. The proposed rectification mechanism is also extended to compressible flows, leading to the first demonstration of rectifying equilibrium gas flows under the Stokes flow regime. While the maximum rectification ratio experimentally obtained in this work is limited to 1.41, a higher value up to 1.76 can be achieved by optimizing the width profile of the asymmetric microchannels.

γ-Graphyne rectifier and NDR tunable by doping, line edge roughness and twist

The armchair γ-graphyne nanoribbon (A-γ-GyNR) based on doping boron and nitrogen atoms in left and right leads, respectively, was proposed as the initial sample of a rectifier device. Afterwards, the next five devices were presented by applying line edge roughness (LER) defect, increasing its roughness, doping concentration, and its position and twisting under six different angles to the center of the initial model. Also, the effect of width was investigated. The computational method for investigating the electronic transfer properties was a combination of the non-equilibrium Green’s function (NEGF) and the tight binding method. The current curve and transmission spectrum revealed the negative differential resistance (NDR) behavior, which underwent the most changes under the influence of LER. Density of state (DOS) peaks indicated that p-orbital had a more significant effect on transmission in all devices; on the other hand, the localization of molecular projected self-consistent Hamiltonian (MPSH) structure in positive biases resulted from the suppression of electron tunneling. Based on the findings, the maximum rectification ratio in the M″3 device, twisted by an angle of 75°, was equal to 5.86 × 108, which was 41.2 times higher than that of the initial sample; the highest NDR value of the M′1 device was 56.

Negative differential resistance and rectification effect of the benzoquinone molecules junction sandwiched between the graphene nanoribbon electrodes

Based on the first-principles calculation method combining the density functional theory (DFT) and the nonequilibrium Green’s function (NEGF) method, the negative differential resistance (NDR) and rectification effect of the benzoquinone molecules junction sandwiched between the graphene nanoribbon electrodes are systematically investigated. The current of the device with the central o-benzoquinone and p-benzoquinone molecule has been demonstrated to decrease with the increase of the bias voltage in the range of [± 0.9 V, ± 1.5 V] and [± 0.6 V, ± 1.1 V], respectively, exhibiting a significant NDR effect. In addition, the interesting NDR effect of the device with the central carbon (C) and nitrogen (N) connected o- and p-benzoquinone molecules has been observed in the bias voltage range of [0.9 V, 1.2 V] and [ $$-0.8$$ V, $$-1.0$$ V] , respectively. The current of the device with the central sulfur (S) and oxygen (O) connected o- and p-benzoquinone molecules should decrease with the increase of the bias voltage at the regime of [0.8 V, 1.0 V] while that should be forbidden when a negative bias voltage is applied, illustrating an interesting rectification effect, and the maximum rectification ratio is observed to be up to 57.85 and 55.85, respectively. The obtained NDR and rectification effect are physically explained from the integral of the transmission coefficient in the bias voltage window and the distribution of the real space charge density, and the demonstrated results are believed to be vital for the designing of the molecular switches, molecular rectifying devices and negative differential resistance devices based on benzoquinone molecules junction.

Tunable solid-state thermal rectification by asymmetric nonlinear radiation.

Thermal rectification is a direction-dependent asymmetric heat transport phenomenon. Here we report the tunable solid-state thermal rectification by asymmetric nonlinear far-field radiation. The asymmetry in thermal conductivity and emissivity of a three-terminal device is realized by sputtering a thin metal film (radiation barrier: niobium, copper, or silver) on the top right half of a polyethylene terephthalate strip (emitter). Both the experiment and finite element analysis are in excellent agreement, revealing a thermal rectification ratio (TR) of 13.0% for the niobium-deposited specimen. The simulation demonstrates that the TR can be further increased to 74.5% by tuning asymmetry in thermal conductivity, emissivity, and surface area. The rectification can also be actively controlled, by gating the environmental temperature, resulting in a maximum TR of 93.1%. This work is applicable for a wide range of temperatures and device sizes, which may find applications in on-demand heat control and thermal logic gates.

Effect of Different Metallic Contacts on the Device Performance of a p-n Heterostructure of a Topological Insulator and Silicon (p-Bi2Te3/n-Si)

This article investigates the performance of the p-Bi <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Te <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> /n-Si heterostructure diode with different metallic contacts. The heterostructure was realized by the thermal coating of a topological insulator (TI) Bi <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Te <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> film on n-Si. The crystal phase study of the Bi <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Te <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> film was done by X-ray diffraction (XRD), while the microstructural and morphological study was done by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The CV characterization for the diode showed almost no hysteresis except for the gold (Au) contact device, which could be due to the trapping of electrons at the interface. The current-voltage (IV) measurement was done in the dark, which confirmed the formation of p-n diode heterostructure. Diode having platinum (Pt) metallic contact exhibited the best ideality factor (n = 7.00), while the diode with gold (Au) contact closely followed it (n = 8.91). The best figure of merit (FOM) ≈ 2.588 was observed for Pt contact device with the maximum rectification ratio (RR) ≈ 442 and majority charge carrier concentration (N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">A</sub> ) = 1.47 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">25</sup> /cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> . The experimental results of I - V for different contact devices were further simulated using the two-diode model and various diode parameters were extracted. The current density- voltage (JV) and local ideality factor-voltage (nV) plots were studied to find the ideality factor and recombination current (J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">02</sub> ) for different metallic contact devices. The Pt contact diode was found to be nearest to the ideal behavior of a diode exhibiting the least recombination current (J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">02</sub> ) = 9.7 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-17</sup> A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> .

Fabrication and characterization of solution processed Al/Sn:ZnO/p-Si photodiodes

This study describes the deposition of ZnO thin films with various Sn doping concentration by a solution-based spin coating method. The effect of Sn doping on structural ZnO thin films and optoelectrical features of ZnO based photodiodes have been investigated. As a result of the structural analysis by XRD and AFM, the thin films showed an amorphous nature and the surface roughness decreasing with Sn doping. The electrical analysis revealed that the fabricated diodes showed a high rectification ratio (RR). The maximum RR value of 4.38 × 104 at ± 4 V and minimum reverse bias current were obtained from SZO10 (%10 Sn doped ZnO). Also, all diodes indicated good photodiode characteristic and the highest responsivity value of 1.68 A/W was obtained from SZO10 as the result of photosensitivity. The obtained results showed that the tin doping improved the electrical and optoelectrical characteristics of the ZnO based diode.