Photovoltaic Platform Research Articles

Hybrid metal nanoantenna 2D-material photovoltaic device

Transition metal dichalcogenides materials such as WeS2 and MoS2 provide an attractive material platform for photovoltaics due to high carrier mobility, tunable band gap, ease of transfer on other substrates. Monolayer/multilayer of these vanderWaals materials is easy to fabricate on a desired substrate either by mechanical exfoliation or by chemical vapor deposition. In this review article, a comprehensive review of an ultra-thin and ultralight design of a photovoltaic system is presented. We describe the most significant methods of fabrication of the monolayers of the 2D materials. Furthermore, we discuss in detail how the interaction of different plasmonic nanostructures leads to an efficient hybrid metal nanoantenna2D- material photovoltaic device.

High‐accuracy voltage regulation method for PV distribution systems

In this Letter, a novel voltage regulation method is proposed for ensuring voltage security in photovoltaic (PV) distribution systems. It is a two-level regulation to reduce overall voltage deviation (VDE) and voltage difference (VDI). Firstly, evaluation indexes for VDE and VDI are built. Then, in order to reduce VDE, primary regulation by sensitivities-based power compensation is developed. Furthermore, in order to reduce VDI, secondary regulation by using PI coordinate compensator is built. Compared with other methods, the proposed method can achieve high regulation accuracy. The effectiveness is verified in a PV platform.

Organic Photovoltaic Sensors for Photocapacitive Stimulation of Voltage‐Gated Ion Channels in Neuroblastoma Cells

AbstractOrganic semiconductors are emerging as promising candidates for novel electrically self‐sufficient photovoltaic prosthetics for neurostimulation, especially for restoration of light sensitivity in degenerate retina. Considering future applications, it is essential to gain fundamental insight into the signaling mechanisms at the organic photosensor–electrolyte–neuron interface. Particularly, targeting voltage‐gated ion channels by a pure photocapacitive stimulation is a preferred therapeutic approach as it avoids redox reactions involved in Faradaic charge injection. The present study investigates whether single neuroblastoma (N2A) cells, grown on a photosensor based on a small molecular squaraine:fullerene photoactive layer blend, optionally covered with silicon dioxide, can be activated by photocapacitive stimulation. Indeed, upon pulsed illumination, a rapid transient photocurrent strongly depolarizes the membrane potential and subsequently activates fast‐responding voltage‐gated sodium channels. The dielectric top coating on the organic layer ensures sufficient capacitive charge injection efficiency while maintaining the rapid response of the device. Due to the high irradiance level required for photocapacitive stimulation, another slower, independent, and unintended, nonelectrical signaling pathway is identified. This activates voltage‐gated potassium channels, presumably by photothermal effects. The present study provides the basis for further improvements on standalone photovoltaic neurostimulating platforms based on organic photoactive layers.

Resonances of enclosed shallow water basins with slender floating elastic bodies

A model for the hydroelastic response of enclosed shallow water basins with floating slender plates of large span, in variable bathymetry is presented. The eigenproblem for the system’s resonant behaviour is formulated in the strong and variational form. Based on the variational form, and special hydroelastic finite elements, a quadratic eigenvalue problem is derived for the eigenfrequencies and eigenmodes of the basin-floating body system. Benchmark examples, for simplified configurations, are used to study the effects of parameters like the plate’s span, position, draft, mass, stiffness and depth of the basin. It is observed that the presence of the plate can alter significantly the eigenstates of the pond if the depth of the basin is relatively small, compared to the plate draft. In such cases the plate span and position play a crucial role. The hydroelastic analysis can be important even in cases where the depth increases and the upper surface elevation differences, in the presence or absence of the floating plate, appear to be less significant. This is due to the importance in accurately calculating the curvature and hence bending moments inside the plate. The proposed model could be relevant to the seiche formation analysis in reservoirs with floating photovoltaic platforms or ice-covered lakes.

Cu2ZnSnS4 solar cells with over 10% power conversion efficiency enabled by heterojunction heat treatment

Sulfide kesterite Cu2ZnSnS4 provides an attractive low-cost, environmentally benign and stable photovoltaic material, yet the record power conversion efficiency for such solar cells has been stagnant at around 9% for years. Severe non-radiative recombination within the heterojunction region is a major cause limiting voltage output and overall performance. Here we report a certified 11% efficiency Cu2ZnSnS4 solar cell with a high 730 mV open-circuit voltage using heat treatment to reduce heterojunction recombination. This heat treatment facilitates elemental inter-diffusion, directly inducing Cd atoms to occupy Zn or Cu lattice sites, and promotes Na accumulation accompanied by local Cu deficiency within the heterojunction region. Consequently, new phases are formed near the hetero-interface and more favourable conduction band alignment is obtained, contributing to reduced non-radiative recombination. Using this approach, we also demonstrate a certified centimetre-scale (1.11 cm2) 10% efficiency Cu2ZnSnS4 photovoltaic device; the first kesterite cell (including selenium-containing) of standard centimetre-size to exceed 10%. The emerging kesterite Cu2ZnSnS4 solar cell offers a potential low-cost, non-toxic, materially abundant platform for next-generation photovoltaics, yet its efficiency has been mired below 10%. Yan et al. now use post-heat treatment of the heterojunction to show device efficiencies that surpass 10%.

Alloy-Controlled Work Function for Enhanced Charge Extraction in All-Inorganic CsPbBr3 Perovskite Solar Cells.

All-inorganic CsPbX3 (X=I, Br) perovskite solar cells are regarded as cost-effective and stable alternatives for next-generation photovoltaics. However, sluggish charge extraction at CsPbX3 /charge-transporting material interfaces, which arises from large interfacial energy differences, have markedly limited the further enhancement of solar cell performance. In this work, the work function (WF) of the back electrode is tuned by doping alloyed PtNi nanowires in carbon ink to promote hole extraction from CsPbBr3 halides, while an intermediate energy by setting carbon quantum dots (CQDs) at TiO2 /CsPbBr3 interface bridges electron transportation. The preliminary results demonstrate that the matching WFs and intermediate energy level markedly reduce charge recombination. A power conversion efficiency of 7.17 % is achieved for the WF-tuned all-inorganic perovskite solar cell, in comparison with 6.10 % for the pristine device, and this is further increased to 7.86 % by simultaneously modifying with CQDs. The high efficiency and improved stability make WF-controlled all-inorganic perovskite solar cells promising to develop advanced photovoltaic platforms.

1 mm3-sized optical neural stimulator based on CMOS integrated photovoltaic power receiver

In this work, we present a simple complementary metal-oxide semiconductor (CMOS)-controlled photovoltaic power-transfer platform that is suitable for very small (less than or equal to 1–2 mm) electronic devices such as implantable health-care devices or distributed nodes for the Internet of Things. We designed a 1.25 mm × 1.25 mm CMOS power receiver chip that contains integrated photovoltaic cells. We characterized the CMOS-integrated power receiver and successfully demonstrated blue light-emitting diode (LED) operation powered by infrared light. Then, we integrated the CMOS chip and a few off-chip components into a 1-mm3 implantable optogenetic stimulator, and demonstrated the operation of the device.

Biodegradable Monocrystalline Silicon Photovoltaic Microcells as Power Supplies for Transient Biomedical Implants

AbstractBioresorbable electronic materials serve as foundations for implantable devices that provide active diagnostic or therapeutic function over a timeframe matched to a biological process, and then disappear within the body to avoid secondary surgical extraction. Approaches to power supply in these physically transient systems are critically important. This paper describes a fully biodegradable, monocrystalline silicon photovoltaic (PV) platform based on microscale cells (microcells) designed to operate at wavelengths with long penetration depths in biological tissues (red and near infrared wavelengths), such that external illumination can provide realistic levels of power. Systematic characterization and theoretical simulations of operation under porcine skin and fat establish a foundational understanding of these systems and their scalability. In vivo studies of a representative platform capable of generating ≈60 µW of electrical power under 4 mm of porcine skin and fat illustrate an ability to operate blue light‐emitting diodes (LEDs) as subdermal implants in rats for 3 d. Here, the PV system fully resorbs after 4 months. Histological analysis reveals that the degradation process introduces no inflammatory responses in the surrounding tissues. The results suggest the potential for using silicon photovoltaic microcells as bioresorbable power supplies for various transient biomedical implants.

Efficiency enhancement of hybridized solar cells through co-sensitization and fast charge extraction by up-converted polyethylene glycol modified carbon quantum dots

Photovoltaics are promising solutions to energy crisis and environmental pollution problems. The dye-sensitized solar cells with mesoscopic structures have attracted growing interests because of zero emissions, easy fabrication, scalable materials and techniques, etc. However, the state-of-the-art dye-sensitized solar cells have narrow spectral absorption for photoelectric conversion and high electron-hole recombination rate under sunlight illumination. Therefore, it is a persistent object to make wide-spectral absorption and fast charge extraction solar cells for energy harvest in both solar and dark-light conditions. To address this issue, we present here experimental realization of a category of solar cells converting visible and near-infrared light into electricity by co-sensitizing photoanode with N719 dye and polyethylene glycol (PEG) modified carbon quantum dots (PEG-m-CQDs), arising from up-conversion and hole-transporting behaviors of PEG-m-CQDs as well as photofluorescence of green-emitting long persistence phosphors. The optimized solar cell yields maximized photoelectric conversion efficiencies of 9.89% and 25.81% under simulated sunlight (air mass 1.5, 100 mW cm−2) illumination and dark conditions, respectively. This work is far from optimization, but the physical proof-of-concept hybridized solar cell may markedly increase electricity generation time and total power output of photovoltaic platforms.

Stretchable and waterproof elastomer-coated organic photovoltaics for washable electronic textile applications

Textile-compatible photovoltaics play a crucial role as a continuous source of energy in wearable devices. In contrast to other types of energy harvester, they can harvest sufficient electricity (on the order of milliwatts) for wearable devices by utilizing the cloth itself as the platform for photovoltaics. Three features are important for textile-compatible photovoltaics, namely environmental stability, sufficient energy efficiency and mechanical robustness. However, achieving these simultaneously remains difficult because of the low gas barrier properties of ultrathin superstrates and substrates. Here, we report on ultraflexible organic photovoltaics coated on both sides with elastomer that simultaneously realize stretchability and stability in water whilst maintaining a high efficiency of 7.9%. The efficiency of double-side-coated devices decreases only by 5.4% after immersion in water for 120 min. Furthermore, the efficiency of the devices remains at 80% of the initial value even after 52% mechanical compression for 20 cycles with 100 min of water exposure. Organic solar cells can be thin, bendable and strechable. Now, Jinno et al. develop flexible organic photovoltaic devices that can also be washed in water and detergent, opening future integration routes into everyday objects such as fabric.

Absorption and transmission of light in III–V nanowire arrays for tandem solar cell applications

III–V semiconductor nanowires are a platform for next-generation photovoltaics. An interesting research direction is to embed a nanowire array in a transparent polymer, either to act as a stand-alone flexible solar cell, or to be stacked on top of a conventional Si bottom cell to create a tandem structure. To optimize the tandem cell performance, high energy photons should be absorbed in the nanowires whereas low energy photons should be transmitted to and absorbed in the Si cell. Here, through optical measurements on 1.95 eV bandgap GaInP nanowire arrays embedded in a polymer membrane, we identify two mechanisms that could be detrimental for the performance of the tandem cell. First, the Au particles used in the nanowire synthesis can absorb >50% of the low-energy photons, leading to a <40% transmittance, even though the Au particles cover <15% of the surface area. The removal of the Au particles can recover the transmission of low energy photons to >80%. Second, after the removal of the Au particles, a 40% reflectance peak shows up due to resonant back-scattering of light from in-plane waveguide modes. To avoid the excitation of these optical modes in the nanowire array, we propose to limit the pitch of the nanowire array.

Chaos Quantum-Behaved Cat Swarm Optimization Algorithm and Its Application in the PV MPPT.

Cat Swarm Optimization (CSO) algorithm was put forward in 2006. Despite a faster convergence speed compared with Particle Swarm Optimization (PSO) algorithm, the application of CSO is greatly limited by the drawback of “premature convergence,” that is, the possibility of trapping in local optimum when dealing with nonlinear optimization problem with a large number of local extreme values. In order to surmount the shortcomings of CSO, Chaos Quantum-behaved Cat Swarm Optimization (CQCSO) algorithm is proposed in this paper. Firstly, Quantum-behaved Cat Swarm Optimization (QCSO) algorithm improves the accuracy of the CSO algorithm, because it is easy to fall into the local optimum in the later stage. Chaos Quantum-behaved Cat Swarm Optimization (CQCSO) algorithm is proposed by introducing tent map for jumping out of local optimum in this paper. Secondly, CQCSO has been applied in the simulation of five different test functions, showing higher accuracy and less time consumption than CSO and QCSO. Finally, photovoltaic MPPT model and experimental platform are established and global maximum power point tracking control strategy is achieved by CQCSO algorithm, the effectiveness and efficiency of which have been verified by both simulation and experiment.

Solar Manager: Acquisition, Treatment and Isolated Photovoltaic System Information Visualization Cloud Platform

This article describes a platform of acquisition, processing and visualization of the behavior for isolated solar systems called SOLAR MANAGER. The recording of measurements was conducted in an isolated photovoltaic installation of the Ambato Technical University Faculty of Electronics Engineering and Industrial Systems. The acquisition system will provide the information necessary for performing maintenance monitoring, operation and supervision through variables such as voltage, current, temperature and humidity system to generate renewable energy remotely from a CLOUD COMPUTING platform. It is intended that the implemented system is economically viable, because the system is developed in open source allowing compete with commercial monitoring systems. The control and monitoring of photovoltaic installations isolated platform - SOLAR MANAGER, in the future one will become a central monitoring and control of all isolated PV plants installed all over the country

Dictating Organolead Perovskite Nanostructure Size Using Silicon Nanotube Templates

A class of alkyl ammonium lead halide structures that readily crystallize as perovskite phases of the generic formula CH3NH3PbX3 have been discovered, and their relative ease of crystallization and formation into robust films have led to the development of an exciting new class of photovoltaic and lasing platforms. To our knowledge, however, synthetic methods that permit an evaluation of the fundamental size dependent properties with the requisite level of control of any of these perovskite structures have not yet been achieved. The key element to achieving feature size control in the synthesis of these perovskite phases is the use of hollow semiconducting silicon nanotubes as templates for perovskite growth; i.e. viewing the nanotube interior as a nanoscale reaction vessel. We have recently reported a facile strategy for the formation of SiNTs of a broadly tunable inner diameter, as well as Si wall thickness. These nanotubes are currently under evaluation for a diverse range of additional uses, such as loading with magnetic nanostructures, drug loading and subsequent delivery, Li storage and discharge phenomena associated with battery technology, etc. In principle, these nanotubes permit structural control of perovskite width through nanotube inner diameter. In this work, we describe the formation of methylammonium lead iodide nanostructures inside porous silicon nanotubes with a wall thickness of 10 nm and possessing inner diameters of either 70 nm or 200 nm. After structural characterization, the photophysical properties of these perovskite nanostructures, in terms of optical absorption and photoluminescence as a function of temperature, are evaluated. Spectroscopic comparisons with relatively larger one-dimensional microwires of the same composition are also carried out. We seek to interrogate not only the presence of size dependent shifts in absorption/emission features associated with a given perovskite structure, but also the effects of physical confinement on possible size-dependent phase behavior of these one dimensional semiconductors.

Comparative analysis of the infield response of five types of photovoltaic modules

Five types of photovoltaic (PV) modules were comparatively analyzed considering the electrical output, efficiency and relative loss in efficiency, based on infield data collected in a temperate mountain climate, over 14 months. The mono-, poly-crystalline silicon, CdTe, CIS and CIGS modules were mounted on two identical platforms, installed close to a row of buildings. Based on the data collected from individual or groups of modules on the two platforms, analyses focused on the photovoltaic output, considering: the mean monthly values; the influence of the neighboring buildings; the influence of the irradiance, temperature and wind in different seasons (winter, summer); the influence of tracking on each PV module type. The qualitative analysis shows that small PV platforms installed in the built environment require accurate investigations on the air currents with influence on snow and frost retention/melting and water vapor condensation. In the temperate climate, with snowy winters and rather warm summers, the best performing modules are of poly-crystalline silicon; among thin film modules, the best output corresponds to CIGS, while the steadiest efficiency corresponds to CdTe. Tracking has a “leveling” effect on the conversion efficiency, making the PV output more predictable during days with preponderant direct solar irradiance.

Rational Strategies for Efficient Perovskite Solar Cells.

A long-standing dream in the large scale application of solar energy conversion is the fabrication of solar cells with high-efficiency and long-term stability at low cost. The realization of such practical goals depends on the architecture, process and key materials because solar cells are typically constructed from multilayer heterostructures of light harvesters, with electron and hole transporting layers as a major component. Recently, inorganic-organic hybrid lead halide perovskites have attracted significant attention as light absorbers for the fabrication of low-cost and high-efficiency solar cells via a solution process. This mainly stems from long-range ambipolar charge transport properties, low exciton binding energies, and suitable band gap tuning by managing the chemical composition. In our pioneering work, a new photovoltaic platform for efficient perovskite solar cells (PSCs) was proposed, which yielded a high power conversion efficiency (PCE) of 12%. The platform consisted of a pillared architecture of a three-dimensional nanocomposite of perovskites fully infiltrating mesoporous TiO2, resulting in the formation of continuous phases and perovskite domains overlaid with a polymeric hole conductor. Since then, the PCE of our PSCs has been rapidly increased from 3% to over 20% certified efficiency. The unprecedented increase in the PCE can be attributed to the effective integration of the advantageous attributes of the refined bicontinuous architecture, deposition process, and composition of perovskite materials. Specifically, the bicontinuous architectures used in the high efficiency comprise a layer of perovskite sandwiched between mesoporous metal-oxide layer, which is a very thinner than that of used in conventional dye-sensitized solar cells, and hole-conducting contact materials with a metal back contact. The mesoporous scaffold can affect the hysteresis under different scan direction in measurements of PSCs. The hysteresis also greatly depends on the cell architecture and perovskite composition. In this Account, we will describe what we do with major aspects including (1) the film morphology through the development of intermediate chemistry retarding the rapid reaction between methylammonium or formamidinium iodide and lead halide (PbI2) for improved perovskite film formation; (2) the phase stability and band gap tuning of the perovskite layer through the materials engineering; (3) the development of electron and hole transporting materials for carrier-selective contacting layers; and (4) the adoption of p-i-n and n-i-p architectures depending on the position of the electron or hole conducting layer in front of incident light. Finally, we will summarize the recent incredible achievements in PSCs, and finally provide challenges facing the future development and commercialization of PSCs.

Mono-Objective Optimization of a Photovoltaic Tracking System with LPF Controllers

The work deals with the optimal design of a single-axis solar tracker, which is used to adjust the daily position of a photovoltaic system in order to capture as much as possible solar radiation. The two main components of the solar tracker (the mechanical device and the control system) have been coupled (integrated) in the concurrent engineering concept. For assuring high stability and robustness, the control system is a cascaded two-loop employing LPF (Low-Pass Filter) controllers. The controlled parameter in the main (external) loop is the daily angle of the photovoltaic platform, while in the secondary (internal) loop the linear velocity in the driving actuator is monitored. The mono-objective optimization problem is described in the following way: to minimize the difference between the imposed and current daily angle (thus preserving a high energetic efficiency of the tracking system), considering the controllers’ gains as independent design parameters.

Double-layer orthogonal-offset photovoltaic platforms

Abstract Photovoltaic panels used for power generation are subject to significant wind loads of concern to mounting systems. A novel method of arranging photovoltaic surface in layers of non-overlapping panels is proposed for tracking systems to reduce wind load forces. The potential of this approach is assessed for double layer systems called DLOOP using Computational Fluid Dynamic turbulence modelling and wind tunnel tests. A consistent pattern of wind-force reduction is found as distance between double layers is increased up to and beyond the scale of the integrated panels’ side length. A 49 panel DLOOP arrangement when tested in high winds had the potential to carry 30% more panels than a single layer arrangement of side by side panels for equivalent wind loading.

Outdoor simultaneous testing of four types of photovoltaic tracked modules

Photovoltaic (PV) systems implemented in the built environment must fulfill supplementary design restrictions related to the limited available space and to architectural integration, thus the need for increased output is a must and tracking, whenever possible, represents a feasible solution. Tracking significantly enhances the amount of solar radiation on the module, including infrared radiation which contributes to their heating and influences the conversion efficiency. These efficiency variations are different, mainly depending on the modules' type (materials). The paper analyses the conversion efficiency of four types of commercial photovoltaic modules (amorphous, mono- and polycrystalline silicon, and CuInS2 (CIS)), simultaneously tested in two in-field setups: on a tracked PV platform and fixed tilt at 45°. The input global radiation and the outdoor temperature are correlated with the variation in the conversion efficiencies, outlining significant differences and the advantages of thin film (CIS) modules. A novel criterion is proposed to evaluate the results: the relative efficiency loss based on the actual and the nominal conversion efficiencies.

Command-Control-Monitoring of a Dual-Axis Tracking Photovoltaic Platform

The main goal of this paper is to present an optimal step-wise orientation program and its implementation way on an outdoor photovoltaic tracking platform developed for testing different types of photovoltaic modules. In the paper there are presented: the functioning mode of the electrical command-control components; the Modbus communication between the components and the monitoring PC; the PC user interface able to allow the changing of the tracking modus and the algorithm used for identifying the optimal tracking program. In the last part several monitoring results, obtained from the tracked vs. fixed PV modules installed in the mountain area Brasov, Romania, are described.