Tandem Structure Research Articles

Tandem achromatic metasurface for waveguide coupling in full-color AR displays.

Waveguide coupling design is one of the most challenging topics in augmented reality (AR) near-eye displays (NED). The primary challenge stems from the necessity to simultaneously address two competing factors: the overall volume of the AR system and the occurrence of chromatic aberration. To address this issue, what we believe to be a novel tandem trilayer achromatic metasurface is specifically designed for waveguide coupling in AR NEDs, capable of achieving an achromatic effect in a nanometer-thin layer. By analyzing the influence of unit structure parameters on the phase delay of input electromagnetic waves, the optimal parameters are determined and the tandem trilayer achromatic metasurface structure is established. Simulation results show that the incident light can be deflected by 45°, 46°, and 45° at wavelengths of 440 nm ∼ 470 nm, 520 nm ∼ 550 nm, and 620 nm ∼ 660 nm, respectively. The angular deviation error of the three primary colors is maintained lower than 1° in the AR waveguide, ensuring a satisfactory achromatic effect. This design provides a new solution for developing ultra-thin and compact optical systems for full-color AR NEDs.

Endurable IGZO/SnSx/IGZO Heterojunction Phototransistor Arrays for Image Sensors.

Optoelectronic devices require stable operation to detect repetitive visual information. In this study, endurable arrays based on heterojunction phototransistors composed of indium-gallium-zinc oxide (IGZO) with a low dark current and tin sulfide (SnSx) capable of absorbing visible light are developed for image sensors. The tandem structure of IGZO/SnSx/IGZO (ISI) enables stable operation under repetitive exposure to visible light by improving the transport ability of the photoexcited carriers through mitigated trap sites and their separation into each IGZO layer. Additionally, the structure promotes recombination by confining the holes. Therefore, the optimal ISI phototransistors exhibit a photoresponsivity of 514.50 A/W and a detectivity of 1.31 × 109 Jones under red light (635 nm) of 1 mW/mm2 and endurable time-dependent photoresponse characteristics, including a slope value of 1.66 × 10-11, without the persistent photoconductivity phenomenon under green light (532 nm) at a frequency of 50 mHz for over 4,000 s. Furthermore, image sensing characteristics of the 6 × 6 arrays based on ISI phototransistors for image sensors are demonstrated by sequentially applying "4" and "2" digit numbers. These technologies contribute to the development of endurable oxide-based optoelectronic devices and provide valuable perspectives on the utility of next-generation image sensors.

Effect of absorbing layer thickness on efficiency solar cells multijunctions vertical based CIGS Using SILVACO TCAD

In this study, we performed numerical simulations using SILVACO-TICAD to analyse microelectronic and photonic structures and identify the optimal device configuration between multi-junction tandem and vertical multi-junction solar cells. We focused on thin-film CIGS (Copper Indium Gallium Selenide) solar cells under normalized conditions (AM1.5G, 0.1 spectral irradiance, and 300 K). The vertical tandem structure analysed consists of three junctions. Multi-junction solar cells offer higher efficiencies than single-junction cells. By combining CGS (Copper Gallium Selenide) with CIGS, about a 10% efficiency improvement is achieved over a vertical multi-junction (Gover A,1974) CIGS-only solar cell. The optimized vertical multi-junction structure showed the following photovoltaic parameters: **short-circuit current density (Jsc) = 32.42 mA/cm², open-circuit voltage (Voc) = 2.52 V, and a conversion efficiency of 34.68%**. This study highlights the potential of multi-junction solar cells, especially when combining different materials, to achieve significant performance improvements over traditional single-junction configurations.

Design and optimization of a low-loss waveguide taper for a narrow-band O-band multiplexer

The fast deployment of high-performance data centers accelerates the development of O-band wavelength division multiplexing (WDM) and its devices. To minimize insertion loss in WDM devices, it is essential to maximize coupling efficiency between optical fibers and waveguides at micro- and nano-scale. In this paper, we propose a low-loss waveguide tapered coupler and its optimization around 1310 nm. The coupler has a vertically placed double-layer rib taper as an intermediate waveguide, and the inverted taper is in a tapered tandem structure. Rib tapers are introduced in the intermediate waveguide and the fiber is coupled to the rib tapers, which are adiabatically reduced in width along the direction of the coupler to vertically reduce the mode size. To minimize footprint, a cascaded inverted taper is introduced. The maximum taper angle per stage corresponding to the long adiabatic taper is first determined. Subsequently, the long tapers are replaced with new shorter tapers. Several parameters are optimized using frequency domain time division (FDTD), including the output waveguide and input surface dimension, the height ratio of rib tapers, the length of inverted tapers, the length of rib tapers, and the tapered profile of tandem structure. The optimization results show that the coupler has an insertion loss of only 0.06 dB at 1310 nm with a device length of 513.4 µm. The two-stage in-plane coupler operates in O-band narrow-band with low insertion loss, offering an efficient solution for coupling fiber to on-chip waveguides.

Inverse design of narrowband thermal emitter with tandem films structures using simulated annealing algorithm

An inverse design method of narrow-band thermal emitter with a tandem films structures is proposed here, which is accomplished by the simulated annealing algorithm. Using this method, two kinds of structures are designed, which peak absorption rate is 0.8261 at 5.34 μm with a Q-factor of 175, and 0.8931 at 3.56 μm with a Q-factor of 132. The electric field distribution within the structure is analyzed using the finite-difference time-domain method (FDTD), and behavior similar to a Tamm plasmon state. The simulation and experiment of the inverse design method shows good agreement. Such inverse design method is very promising in mid-infrared simulator and detection.

Simulating High‐Efficiency, Lead‐Free Inorganic‐Organic Perovskite Tandem Solar Cells with over 46% Efficiency

AbstractPerovskite‐based tandem solar cells (SCs) show significant potential for improving efficiency. In this study, three configurations were designed and optimized: a top cell (ITO/ZnSe/CH3NH3GeI3/CuSCN/Ni), a bottom cell (ITO/ZnSe/CH3NH3SnI3/CuI/Ni), and a tandem cell combining both. Using SCAPS‐1D, the study evaluated how the absorber layer thickness, doping concentration, and defect density affected photovoltaic (PV) performance. It also explored the influence of doping in the back surface field (BSF), interface defect densities, temperature, and back contact work function. The top cell achieved a power conversion efficiency (PCE) of 28.47%, with an open‐circuit voltage (VOC) of 1.21 V, a short‐circuit current density (JSC) of 27.17 mA/cm2, and a fill factor (FF) of 86.24%. The bottom cell reached a PCE of 18.46%, with a VOC of 0.83 V, a JSC of 27.17 mA/cm2, and an FF of 81.839%. The optimized tandem structure demonstrated a notably higher efficiency of 46.89%, with a JSC of 27.17 mA/cm2, a VOC of 2.04 V, and an FF of 84.31%. These results suggest the proposed CH3NH3GeI3/CH3NH3SnI3 tandem design could pave the way for efficient, eco‐friendly, and cost‐effective PV cells in a near future.

Tandem structure neural network-based channel power optimization in wavelength-division multiplexing systems

For C-band wavelength-division multiplexing (WDM) transmission systems, achieving balanced output channel power is a practical goal for performance maintenance, given the moderate fiber nonlinearity and sometimes outdated control and monitoring devices in these deployed systems. To accomplish this, we propose a digital twin (DT)-based tandem neural network (NN) structure for optimizing launch power profile. The proposed structure consists of two components: an optimization NN, which generates the optimized launched channel power based on a target output power profile, and a forward DT NN, pre-trained to predict output power profile after multi-span transmission. The proposed method enables fast and efficient launch power optimization on simulated links with arbitrary channel loadings and has been validated using open-source experimental data from links with heterogeneous spans and naked amplifiers. The power profile ripple can be reduced from more than 20 dB to 1.2 dB, providing an effective solution for practical C-band WDM systems.

(Invited) Development of High-Efficiency Transparent Cu2O Top Cells for Tandem Photovoltaics with Efficiency Exceeding 30%

Solar cells with high power generation efficiency are expected to be used in mobility applications that require high power output in a limited footprint, such as electric vehicles (EVs) and high-altitude platform stations (HAPS), as well as in current products for housing and industrial applications. A tandem structure is an effective option for high-efficiency solar cells, and various combinations of solar cells have been proposed as the top and bottom cells, including InGaP/GaAs and perovskite/Si. Our proposed tandem solar cell consists of a transparent cuprous oxide (Cu2O) top cell and a crystalline Si bottom cell and is a promising candidate for the next generation of tandem solar cells because of its combination of high efficiency and low cost. High tandem efficiency of 30% or higher is required for various advanced applications such as mobility. Cu2O has a wide bandgap of 2.1 eV, and its spectral sensitivity complements that of crystalline Si, so high bottom-cell efficiency can be achieved. By using Cu2O in the top cell, the Si bottom cell can be expected to have an efficiency of 20% due to long-wavelength light transmitted through Cu2O, and by generating an efficiency of 10% in the Cu2O top cell, a tandem efficiency exceeding 30% is within sight. Cu2O is a low-cost material because it consists of the abundant elements copper and oxygen. Also, it can be formed on inexpensive glass substrates by low-cost manufacturing processes such as sputtering. We have established a technology to deposit high-quality Cu2O thin films as a single phase on transparent electrodes by reactive sputtering. By precisely adjusting the oxygen gas flow rate and substrate temperature, Cu and CuO present as different phases could be removed and a metastable Cu2O phase selectively deposited. A top cell using this low-defect Cu2O as the optical absorption layer has achieved an efficiency of 8.4% [1]. In this paper, we report on a Cu2O top cell that exhibits the world's highest efficiency of 10.5%, which was achieved by improving the short-circuit current density (Jsc) and the open-circuit voltage (Voc). By increasing the size of the Cu2O top cell by a factor of about 3, the area ratio of the dead area at the cell edge to the power-generating area was reduced. We expect that our Cu2O film has a long carrier diffusion length, and thus when the cell area is small, many carriers diffuse to the cell edge face and recombine. By contrast, a larger cell area increases the number of carriers that can contribute to power generation without carriers reaching the cell edge face. Device simulations showed that there were many interfacial defects between p-type Cu2O and n-type Ga2O3, which reduced Voc. Therefore, a unique passivation layer was introduced at the pn interface. This suppressed the interfacial defects and increased Voc by about 0.1 V compared with the conventional cell. The measured efficiency of 10.5% for the Cu2O top cell exceeds our milestone target of 10% for top-cell efficiency, which is required to achieve tandem efficiency of 30%.This work is based on results obtained from a project commissioned by the New Energy and Industrial Technology Development Organization (NEDO).[1] S. Shibasaki, Y. Honishi, N. Nakagawa, M. Yamazaki, Y. Mizuno, Y. Nishida, K. Sugimoto, and K. Yamamoto, "Highly transparent Cu2O absorbing layer for thin film solar cells," Appl. Phys. Lett. 119, 242102 (2021).

(Invited) Tin-Based Perovskite Solar Cells and Development to All-Perovskite Tandem Solar Cells

The efficiency of Lead perovskite solar cells (Pb-PVK-PV) is now 26.1 % which is close to that of silicon solar cells (26.8%) (1). The research has been shifted to the fabrication of the large modules and the module stability. After the research of the Pb-PVK-PV, Tin perovskite solar cells (Sn-PVK-PV) are attracting attentions. The bandgap of MAPbI3 and MASnI3 is about 1.55 eV and 1.35 eV, respectively. When the Pb-PVK is mixed with the Sn-PVK, the bandgap becomes narrower (1.2 eV) than that of each solar cell. The SnPb alloyed perovskite (SnPb-PVK-PV) covers the bandgap from 1.5 eV to 1.0 eV, which contracts to the Pb-PVK having light absorption of visible region. The tandem structure is composed of the top cell with the bandgap of 1.6-1.8 eV and the bottom cell with the bandgap:1.1-1.3 eV. The SnPb-PVK fulfills the requirement of the bottom cell. The efficiency of the perovskite/Si tandem solar cells is now 33.9% (1) and that of all-perovskite tandem solar cells consisting of Sn-PVK-PV as the top cell and SnPb-PVK-PV as the bottom cells is 29.1 %. This presentation focusses on the latter tandem solar cells. Roughly speaking, to enhance the efficiency of the tandem cell, the current matching of the bottom cell and the top cell, the efficiency-enhancement of the top and bottom cell, and the optimization of charge recombination rate at the interconnecting layer. Before talking about SnPb-PVK-PV, the efficiency-enhancement of Pb-free Sn PVK-PV are discussed. For both of the Sn-PVK-PV and the SnPb-PVK-PV, Sn4+ in the perovskite layer decreases the efficiency. Sn4+ may be contained in the row material and is formed in the perovskite inks which contains DMSO working as oxidant. Sn metal deposition at both side of the Sn-PVK layer enhance the efficiency(2). In addition, we have reported the addition of Ge ions, the passivation of the Sn-PVK layer with Lewis-base such as ethylenediamine, and the band-offset optimization between the Sn-PVK and the electron transport layer (ETL) are effective to enhance the efficiency (3). 15.3 % efficiency is reported. In the same way, the efficiency of the SnPb-PVK-PV was enhanced to 23.3 %(4). In addition, the thermal stability (85 ℃, 1000 h) of the SnPb-PVK-PV was significantly improved by adding Ge ion to the perovskite ink and inserting ion-migration-blocking layer. The interconnecting layer must be designed so that the holes formed in the bottom layer and the electrons formed in the top layer could be effectively recombined at the interconnection layer. For examples, Bottom/GO/ALD SnOx/Top, Bottom/AZO/ALD SnOx/Top, Bottom/Au/ALD-SnOx/Top, Bottom/ITO/ALD-SnOx/Top, Bottom/ALD -SnOx/Top have been reported as the interconnection layer. We report the IZO as the interconnection layer prepared by optimizing the sputtering condition (5). The IZO was designed so that hole-injection rate from the bottom cell to the IZO is close to the electro injection from the top cell to the IZO. The efficiency of 26.8 % is reported. To aim at the efficiency over 30%, the development on the four items listed before is further needed.Reference: [1] Martin A. Green, eta al., Prog. Photovolt. Res. Appl, 2023, 31, 651-663, Efficiency Table 62. [2] L. Wang, S. Hayase, et al., Angewandte, 2023, 135, e202307228. [3] Hayase, Shuzi, Sn-based Halide Perovskite Solar Cells, Chapter 10, 293-319, 2021, Perovskite Photovoltaics and Optoelectronics, Edited by Miyasaka, T., Eiley-VCH. [4] K. Gaurav and S. Hayase, et al., ACS Energy Lett., 2022, 7, 3, 966–974. [5] b. Fuan and S. Hayase, et.al., ACS Energy Letters, 2023, 8, 3852-3859.

High Local CO Concentration Generated By Delicate Control of Au Nanoparticles from Au-Cu2o Tandem Catalyst Boosts Electrochemical CO2 Conversion into Value-Added C2+ Products

The electrochemical reduction of carbon dioxide (CO2RR) holds promise for carbon capture and utilization (CCU), aiming to produce carbon-neutral fuels and valuable chemical intermediates. Copper (Cu) is recognized as the primary metallic catalyst facilitating C-C coupling reactions to yield multi-carbon compounds.Many researchers have been developing Cu catalysts, such as oxide-derived Cu (OD-Cu), and tandem catalysts to increase the kinetics of C-C coupling. The investigation of tandem catalysts, especially those derived from oxides of copper (OD-Cu), has been conducted to improve selectivity towards multi-carbon compounds like ethylene and ethanol.Nonetheless, the effect of the loading structure of the CO-producing catalyst within the tandem catalyst on CO2RR performance has not been fully explored. In this study, we synthesized Au nanoparticles with different sizes and loading densities on Cu2O through the galvanic replacement reaction and examined their influence on CO2RR properties.Tandem catalysts containing smaller Au nanoparticles demonstrated heightened activity in the electrochemical CO2RR, leading to an anodic shift in potential. Additionally, tandem catalysts with smaller Au nanoparticles exhibited improved Faradaic efficiencies (FEs) and partial current densities (PCDs) for C2+ compounds. The tandem catalysts with larger Au nanoparticles also showed better CO2RR performance than the original OD-Cu; however, it was found that CO2RR results of the tandem catalysts with a small size of Au nanoparticles were superior to those with large size of Au nanoparticles.Interestingly, the FEs and PCDs of n-propanol, a C3 product, increased as the coverage of Au nanoparticles increased. This behavior contrasts with the case of ethylene and ethanol. The maximum Faradaic efficiencies (FEs) of these C2 products from tandem catalysts did not exceed those from OD-Cu.The effectiveness of the tandem effect relies on the localized concentration of CO, heightened by the CO-producing catalyst situated on the confined OD-Cu surface. The improvement of the selectivity towards the C3 product may come from the interface between the Au nanoparticles and OD-Cu, where the C1-C2 coupling reaction is favorable.We utilized a Nickel single-atom catalyst (Ni-SAC) to create a high local concentration of CO within the catalyst layer. Despite this, we did not observe any tandem effect. This suggests that the proximity between CO active sites and C2+ active sites plays a crucial role in triggering the CO spillover effect. Our results shed light on a strategy for constructing efficient tandem structures in CO2RR.

Improving Solar Cell Efficiency of Silicon and Silicon Tandem Structure by Using Surface Modification

Silicon heterojunction (SHJ) solar cells face challenges in maximizing energy capture due to limitations in light collection and surface passivation. To address this, the use of SHJ tandem solar cells in a back‐to‐back configuration is explored, allowing illumination from both sides to enhance light absorption and energy generation. This study aims to improve the stability and efficiency of these cells through Al2O3 and Nafion surface treatments. Al2O3 is deposited to enhance bifacial light collection, while Nafion is applied for surface passivation to increase the fill factor (FF). The method involves adding 0.1–0.6 units of incident light to the rear of the cells to evaluate the effects of these treatments. The results show a 2.06% increase in efficiency with Al2O3 and a 1.72% improvement with Nafion under standard illumination conditions. The optimized tandem SHJ with Al2O3 and Nafion achieves a Jsc of 62.01 mA cm−2, Voc of 650.63 mV, FF of 76.49%, and an efficiency of 30.86%. These findings demonstrate the significant potential of these surface treatments to enhance the overall performance of bifacial back‐to‐back tandem SHJ solar cells.

A straight-arch-straight beam tandem quasi-zero stiffness structure

Extremely low dynamic stiffness is essential for the successful utilization of quasi-zero stiffness (QZS) structures for vibration isolation, energy harvesting, and micromechanical sensing. However, most conventional QZS structures are based on a parallel connection of positive and negative stiffness mechanisms, which poses challenges for stiffness matching, structure design, and fabrication. We propose a QZS structure based on a straight-arch-straight (SAS) tandem connection, in which the integrated design of the structure overcomes the problem of stiffness matching, and more importantly, the simple design of the structure greatly reduces the difficulty of fabrication and enables the design of a wide range of load-carrying capacity by only adjust the ratio of the length of the straight beam to the arch and the ratio of the height of the arch to the thickness. The symmetric deformation of the SAS structure extends the working range of the QZS structure, which can be further extended several times or divided into several different QZS intervals by connecting several identical or different SAS units in parallel. The experimental results show that the SAS structure has excellent vibration isolation performance in the low-frequency region, and more importantly, the low preload requirement also provides an important reference for structural design in the field of micromechanical sensing.

Enhanced efficiency of carbon based all perovskite tandem solar cells via cubic plasmonic metallic nanoparticles with dielectric nano shells

This study investigates a carbon-based all-perovskite tandem solar cell (AP-TSC) with the structure ITO, SnO₂, Cs₀.₂FA₀.₈Pb(I₀.₇Br₀.₃)₃, WS₂, MoO₃, ITO, C₆₀, MAPb₀.₅Sn₀.₅I₃, PEDOT: PSS, Carbon. The bandgap configuration of the cell is 1.75 eV/1.17 eV, which is theoretically limited to 36% efficiency. The effectiveness of embedding cubic plasmonic metallic nanoparticles (NPs) made of Gold (Au) and Silver (Ag) within the absorber layers to eliminate the requirement for thicker absorber layers, decrease manufacturing costs and Pb toxicity is demonstrated in our analysis. This analysis was conducted using 3D Finite Element Method (FEM) simulations for both optical and electrical calculations. Prior to delving into the primary investigation of the tandem structure, a validation simulation was conducted to demonstrate the accuracy and reliability of the simulations. Notably, the efficiency mismatch observed during the validation simulation, specifically in relation to the incorporation of metallic nanoparticles (NPs), amounted to a mere 0.01%. To mitigate the potential issues of direct contact between metallic NPs and perovskite materials, such as increased thermal and chemical instability and recombination at the NP surface, a 5 nm dielectric shell was applied to the NPs. The incorporation of cubic core-shell Ag NPs resulted in a 15.32% enhancement in short-circuit current density, from 16.39 mA/cm² to 18.90 mA/cm², and a 15.68% increase in overall efficiency, from 26.9 to 31.12%. This research paves the way for the integration of core-shell metallic NPs in AP-TSCs, highlighting a significant potential for efficiency and stability improvements. In a dedicated section the band alignment of the sub-cell was addressed. Additionally, a thermal investigation of the proposed tandem structure was conducted, demonstrating the robustness of the proposed AP-TSC. Finally, the sensitivity analyses related to input parameters and the challenges associated with large-scale fabrication of the proposed AP-TSC were extensively discussed.

Tuning Perovskite Crystal Growth Dynamics Using Additives on Textured Silicon Substrates

Double‐sided textured silicon solar cells with micrometer‐sized pyramid structure are used as bottom cells in monolithic tandem structures to decrease reflection losses. As top cell material, frequently perovskites are used. In this work, various additives are investigated to enhance the perovskite absorber quality, as a top cell fabricated using the hybrid route. In the context of the hybrid route, it is found that urea or methylammonium chloride (MACl) can effectively increase the grain size and improve the absorber quality, while formamidinium chloride (FACl) cannot. With urea, the crystallization can be tuned without leaving any voids in the film (unlike MACl). However, when annealed at a high annealing temperature, the excessive crystal growth with urea causes non‐conformal coating and high defect density. By adjusting the annealing conditions and additive concentration, the crystal growth of the perovskite top cell on the micrometer‐sized silicon pyramids can be fine‐tuned, ensuring that the perovskite layer conformally coated the pyramids. The use of additives not only improves crystallization but also enhances the conversion of the inorganics, particularly at the hole transport layer (HTL) interface. Moreover, this work contributes to a better understanding of perovskite crystallization dynamics and how to control it, especially on textured substrates.

Accordion-Structured Hydrogel Battery Capable of Maintaining Ion Gradients for Extended Periods.

Inspired by the electric eel, biomimetic, biocompatible energy storage, and power generation technologies show promise for applications in portable and wearable electronic devices by mimicking the electric cell tandem structure of the electric eel and utilizing ionic gradients between hydrogel compartments to generate electricity. Previously, inspired by the unique morphology of the torpedo fish, an artificial flexible power source that can output a large current was introduced. This power source uses a hydrogel-infused paper hybrid to create, accordionize, and reconfigure arbitrary-sized gel films in series and parallel, and the power output of the flexible battery was significantly enhanced. However, maintaining the ionic gradient of hydrogel batteries during storage remains a challenge. Here, by borrowing the isolation properties of the accordion structure, we propose a unique paper accordion structure design to fabricate an Accordion-Structured Hydrogel Battery (ASHB). Pretreatment of hydrogel-injected paper strips improved storage stability and maintained the ionic gradient of hydrogel cells in the nonworking state, so that the cell's gradient retention time after the assembly is completed is increased by at least 30 h compared to stacking, and its per-cell operating voltage is still able to reach. The design also makes the assembly and use of flexible batteries more modular and holistic. In the future, it may be possible to power the cells with ions generated by the human body or the metabolites of living organisms, leading to the development of more efficient, sustainable, and eco-friendly power solutions.

Improving current-matching in textured perovskite/silicon tandem solar cells via a thickness control strategy

This study presents an analysis of a two-terminal tandem solar cell that integrates metal-doped, lead-free double Cs2AgBi0.75Sb0.25Br6 perovskite with silicon to enhance overall energy conversion efficiency. This study explores how the thicknesses of the top and bottom sub-cells affect current-matching in two-terminal tandem perovskite/silicon solar cells with two separate planar and textured configurations. Using numerical modeling in MATLAB, and considering dominant recombination effects, we calculated the performance parameters of the device. We investigated the optical and electrical properties of textured tandem structures, focusing on current- matching and the influence of layer thickness on device performance. Given the complexity, time, and expense involved in constructing tandem solar cells, being able to analytically determine the thickness at which current-matching occurs can be highly advantageous. This approach offers the benefit of providing a precise analytical relationship for this purpose. Our findings demonstrate that increasing the top cell thickness enhances current density and power conversion efficiency, but at the cost of the bottom cell’s efficiency due to increased light absorption. Moreover, we discovered a nearly linear behavior between the thickness of the top and bottom cells for achieving current-matching. The study highlights the critical balance required to optimize layer thicknesses, thereby improving the design and performance of tandem solar cells. These insights are significant as they pave the way for more efficient and cost-effective tandem solar cell designs in the future, potentially accelerating the adoption of advanced photovoltaic technologies. The results show good agreement with experimental data, validating our model.

Harnessing SWCNT absorber based efficient CH3NH3PbI3 perovskite solar cells

This paper investigates the effect of incorporating a single-walled carbon nanotubes (SWCNTs) layer into the perovskite solar cell (PSC) structure as an effective technique to boost energy harvesting. The proposed PSC structure utilizes the SWCNTs layer underneath the CH3NH3PbI3 perovskite layer as an absorbing layer forming a novel design of (ITO/SnO2/CH3NH3PbI3/SWCNTs/NiOx/C) half tandem PSC structure. The suggested PSC structure is numerically analyzed using finite element method (FEM). The effects of varying thickness and doping concentration of the added layer and the material of rear electrode are investigated to maximize the power conversion efficiency (PCE) of the suggested PSC. Results of the 3D opto-electrical study and the energy bandgap analysis confirm that utilizing a 680 nm SWCNTs layer with doping concentration of 1.1 × 1020 cm-3 beneath a 150 nm perovskite layer enhances the PCE and short circuit current density (JSC) to 25.6%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$25.6\\%$$\\end{document} and 31.201mA/cm2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$31.201 mA/{cm}^{2}$$\\end{document}, respectively due to the improving of the PSC absorption by 27.65%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$27.65\\%$$\\end{document}. Higher performance of the proposed PSC has been achieved by using gold (Au) electrode instead of carbon (C) one, causing total enhancement of PCE and JSC of 6.185%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$6.185\\%$$\\end{document} and 9.18mA/cm2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$9.18\\;mA/cm^{2}$$\\end{document}, respectively over their values for (ITO/SnO2/CH3NH3PbI3/P3HT/NiOx/C) structure reported in previously published literature. The proposed design can be considered as an efficient alternative to the conventional PSC owing to its higher performance and reduced toxicity.

Study on pressure fluctuation characteristics of the mixed-flow pump with the tandem misaligned blade structure

Abstract As supporting equipment for deep-sea oil and gas resource exploitation, how to improve the transmission performance and stability of the impeller of the mixed-flow pump (MFP) has become a key technical problem. This paper focuses on studying the impeller blade of the MFP. Based on the blade optimization technology, four different tandem misaligned blade (TMB) angle schemes of α=0°,15°,45°,75° are proposed. The SST k-ω turbulence model is used to simulate the different blade angles under the pure liquid condition. The pressure pulsation of the MFP and the blade load distribution are studied. This result show that the TMB structure increases the pressure fluctuation inside the MFP. The pressure coefficient inside the impeller exhibits a more consistent pattern at an angle of α=45° compared to other angles, and the internal flow field of the MFP exhibits most stable. From this analysis of blade load distribution, TMBs have a greater effect on the pressure surface of the front blade of the MFP. When α=15°, the best pressurization performance of the MFP. This study may serve as a benchmark for subsequent iterations of optimizing the MFP’s model and hydraulic design.

8.36% Efficient CZTS Solar Cells on Transparent Electrode via Solution Processing

High‐bandgap Cu2ZnSnS4 (CZTS) thin film solar cells on transparent electrodes show favorable characteristics for new photovoltaic application scenarios including building‐integrated photovoltaics, vehicle‐integrated photovoltaics, and top cell for tandem structure. However, the efficiency of pure sulfide kesterite CZTS thin film solar cells on transparent substrates lags behind that on traditional Mo substrates. Herein, fabrication of high‐quality CZTS absorber films and efficient solar cells on fluorine‐doped tin oxide substrates from dimethyl sulfoxide solution is reported. The formation of harmful secondary phases in CZTS film is suppressed by simply adjusting the chemical stoichiometry in the precursor solution, leading to the development of 5.88% CZTS solar cells. Sodium (Na) doping further promotes grain growth and suppresses secondary phase, contributing to the reduced interface recombination and improved device performance. A champion device with an efficiency of 8.36% has been achieved with 1% Na doping, underscoring the significance of the solution process in achieving highly efficient kesterite solar cells on transparent electrodes.

Delicate control of a gold-copper oxide tandem structure enables the efficient production of high-value chemicals by electrochemical carbon dioxide reduction

The electrochemical carbon dioxide reduction reaction (CO2RR) has substantial potential for carbon capture and utilization (CCU), aiming to produce carbon-neutral fuels and valuable chemical feedstocks. Copper (Cu) is recognized as the primary metal catalyst capable of facilitating C-C coupling and producing multi-carbon compounds. The tandem catalyst approach, particularly the oxide-derived Cu (OD-Cu)-based tandem catalyst, has been reported to improve the selectivity for multicarbon compounds such as ethylene and ethanol. However, the impact of the loading structure of the CO-producing catalyst in the tandem catalyst on CO2RR performance has not been thoroughly investigated. In this study, we developed Au nanoparticles with different sizes and loading densities on Cu2O and investigated their CO2RR properties. Tandem catalysts featuring smaller Au nanoparticles exhibited increased activity in the electrochemical CO2RR, resulting in an anodic shift in the potential. Improved Faradaic efficiencies (FEs) and partial current densities (PCDs) of C2+ were also observed for tandem catalysts with smaller Au nanoparticles. Remarkably, the FE and PCD of n-propanol increased as the coverage of Au nanoparticles increased, in contrast to those of C2 products such as ethylene and ethanol. The effectiveness of the tandem effect depends on the increase in local CO concentration facilitated by the CO-generating catalyst on the confined OD-Cu surface. Our research presents a strategy for constructing a productive tandem structure for the CO2RR.