Tandem Structure Research Articles

High performance perovskite-silicon tandem solar cells

साधारण संविरचन तकनीक के साथ-साथ सौर ऊर्जा को विद्युत् ऊर्जा में परिवर्तित करने की उच्च दक्षता से सुसज्जित पेरोवस्काइट-सिलिकॉन अनुबद्ध सौर प्रौद्योगिकी को सौर ऊर्जा के क्षेत्र में एक आकर्षक और संभावनापूर्ण विकल्प के रूप में देखा जा रहा है। एक से अधिक संधि (junction)वाले पेरोवस्काइट-सिलिकॉन अनुबद्ध सौर सेल (perovskite-Si tandem solar cell) संरचना में कार्यदक्षता एकल संधि सौर सेल की प्रायोगिक दक्षता सीमा से अधिक प्राप्त करते है | कार्बनिक-अकार्बनिक लेड हैलाइड पेरोवस्काइट फोटोवोल्टीय प्रौद्योगिकी से उच्च कार्य क्षमता की रिपोर्ट की गयी है | कम लागत, साधारण एवं सरल निर्माण तकनीक से बना हुआ पेरोवस्काइट सौर युक्ति बहुत हल्का,लचीला व अर्ध-पारदर्शी आदि विशेषताओं से निहित है | यह सौर सेल नम्य सब्सट्रेट पर निर्माण की अनुकूलताओं एवं सामग्रियों के चौड़े पटल मुद्रण से परिपूर्ण होने के कारण औद्योगिकीकरण हेतु उपर्युक्त है | हालांकि पेरोवस्काइट में तापीय अस्थिरता और नमी संवेदनशीलता अभी भी सिलिकॉन सामग्री की तुलना में अत्यधिक है। अनुबद्ध संरचना में पेरोवस्काइट सक्रीय अवशोषक परत ऊपर तथा सिलिकॉन तत्व नीचे रहता है, जिसका बैंड अंतराल क्रमशः 1.54 eV, 1.12 eV है| दो दशक के समयोपरांत भी प्रचलित सिलिकॉन सौर सेल प्रौद्योगिकी की दक्षता अधिकतम लगभग 26 % पर अटकी हुई है | इसी समस्या के समाधान के लिए पेरोवस्काइट-सिलिकॉन अनुबद्ध सौर सेल एक विकल्प के रूप में संभावित है |पेरोवस्काइट-सिलिकॉन अनुबद्ध सौर सेल का प्रकाशीय एवं विद्युतीय अध्ययन स्कैप्स-1डी (SCAPS-1D) अनुकारी तकनीक से किया गया है | अनुबद्ध सौर सेल संरचना TCO/TiO 2 /CH 3 NH 3 PbI 3 /PEDOT:PSS/c-Si(n)/c-Si(p)/c-Si (p+)/Ag में खुला परिपथ वोल्टेज 1.56 V, लघु परिपथ करंट घनत्व 23.7mA/cm 2 , फिल फैक्टर 84.76 % एवं सौर स्पेक्ट्रम के फ़िल्टरीकरण के पश्चात 30.7% दक्षता प्राप्त की गयी है | अनुबद्ध सौर सेल में सिलिकॉन एवं पेरोवस्काइट परत की मोटाई से कार्य प्रदर्शन पर पड़ने वाले प्रभाव का भी अध्ययन किया गया है । Equipped with simple fabrication and efficient technique of converting solar energy into electricity, perovskite-silicon tandem solar technology is being seen as an attractive and promising option in the field of solar energy. Perovskite-Si tandem solar cell structures with multiple junctions achieve efficiency higher than the experimental efficiency limits of a single p-n junction solar cell. Even after two decades, the efficiency of the prevailing silicon solar cell technology is stuck at a maximum of about 26%. Perovskite-silicon tandem solar cells are a possible alternative to this problem. High efficiency is recently reported by using organic-inorganic lead halide perovskite. Perovskite solar device made from low cost and simple manufacturing process, possess inherent characteristics like light in weight, flexible, semi-transparent etc.This solar cell is suitable for industrialization due to its adaptability to fabrication on flexible substrates and compatible with large-scale solution processing such as roll-roll printing of the materials. The thermal instability and moisture sensitivity in perovskite materials are still under-performed when compared to silicon materials. The numerical simulation of perovskite-Si tandem solar cells has been performed. The perovskite active absorber layer is placed at the top and the silicon at the bottom, with band gaps of 1.54 eV, 1.12 eV respectively. The optical and electrical studies of perovskite-silicon tandem solar cells have been done using SCAPS-1D simulation technique. Tandem solar cell structure TCO/TiO 2 /CH 3 NH 3 PbI 3 /PEDOT:PSS/c-Si(n)/c-Si(p)/c-Si(p+)/Ag has open circuit voltage 1.56 V, short circuit current density 23.7mA/cm2, Fill factor is 84.76% and efficiency is 30.7% (after filtration of solar spectrum). The effect of thickness of silicon and perovskite layer on performance in tandem solar cell has also been studied.

Design of high efficiency perovskite/silicon tandem solar cells based on plasmonic enhancement of metal nanosphere

Perovskite/silicon tandem solar cells, by combining perovskite as a top absorber material and crystalline silicon as a bottom absorber material, can expand and enhance the utilization of solar spectrum. Therefore, such a tandem structure shows great potential to break through the Shockley-Queisser (SQ) limit of 31%－33% for single-junction (SJ) solar cells and is considered as one of the most promising approaches to achieving the higher performance in photoelectric conversion of solar cells. Reducing the optical losses from the surface and interfaces of cell device and making more photons propagate into the active layers are the key factors for achieving the goal. In this paper, the enhancement of spectral response and energy conversion efficiency of perovskite/silicon tandem solar cells depending on Au, Ag, Cu, Al nanosphere are studied by using the finite difference time domain method and rigorous coupled-wave analysis. The results show that owing to the introduction of metal nanosphere, the transmittance of photons propagating into the active material is promoted significantly. Therefore, the cell device achieves an apparent increase both in total absorbance and in quantum efficiency. The observed weighted average transmittance and energy conversion efficiency are increased from 73.16% and 23.09% to 79.15% and 24.97%, respectively, with an 8.14% improvement for the perovskite/silicon tandem solar cells coated with the optimized Al nanospheres.

Tandem Organic Solar Cell with 20.2% Efficiency

<h2>Summary</h2> As a promising strategy for enhancing light utilization, constructing cell with tandem structure exhibits great potential in achieving high efficiency, which encourages the field of organic solar cells. Here, we develop an advanced interconnecting layer for tandem organic solar cell, which is composed of electron beam evaporated TiO_x and PEDOT:PSS. By using electron beam evaporation, a sharp, smooth, and dense TiO_x/PEDOT:PSS interface is obtained. By exquisite controlling the O₂ flux during evaporation, efficient electron extraction and low Schottky barrier are obtained in PBDB-TF:GS-ISO/TiO_1.76 and TiO_1.76/PEDOT:PSS, which guarantee the charge recombination between two subcells. The tandem cell with interconnecting layer of TiO_1.76/PEDOT:PSS shows 20.27% efficiency, which is certified as 20.0% by National Institute of Metrology, China. Therefore, our result marks the arrival of 20% era in the field of organic solar cells.

Performance Comparison of Different Hole Transport Layer Configurations in a Perovskite-based Solar Cell using SCAPS-1D Simulation

Due to the solar cell industry, environmentally friendly and low-cost electricity generation processes, the use of non-renewable energy sources, especially fossil fuels, is developing day by day. Among the different solar cells under use, perovskite solar cells have recently experienced rapid growth in research due to their high performance and low production costs at the same time. Perovskite solar cells typically consist of some main layers such as absorbent, carrier layers and electrodes. The hole transport layer (HTL) is very important in the perovskite solar cell structure due to its important role in cell performance. The light absorbed by the perovskite layer leads to the formation of electrons and holes. These load carriers are then transported to the electrodes by the electron and hole transport layers. There are several types of HTL, such as small molecules in the cell structure, polymeric and inorganic HTLs. In addition, these different options can be in various configurations such as tandem, composite and single structures. In this study, three common HTL types, Spiro-OMeTAD, P3HT and Cu2O, were studied and their effects on cell performance in different composite, tandem and single forms were investigated and their results were compared. These comparisons were made in the simulation environment in SCAPS-1D software. The final results showed approximately the best 27% efficiency of the use of tandem structure in the HTL configuration with Spiro-OMeTAD and P3HT in the special perovskite solar cell created in this study.

High temperature annealing effects on optical performance of TiAlN-based solar selective absorber with TiN IR reflector

Higher operating temperature of concentrating solar power plant could help to improving the solar-electricity conversion efficiency. However, solar selective absorber with stability higher than 700 °C is still lacking. Here, we explored the potential of a tandem structure absorber of TiN/Ti0.5Al0.5N/Ti0.33Al0.67N/CrAlSiO. The as-deposited tandem absorber had a solar selectivity of 0.887/0.134, which was maintained at 800 °C for 1 h. With the annealing temperature increasing from 800 °C to 1000 °C, the solar absorptance first slowly decreased from 0.887 to 0.866, then dramatically decreased to 0.7 after annealing at 1100 °C. Optical simulation indicated that thermal annealing would induced higher optical constants both for the Ti0.5Al0.5N and Ti0.33Al0.67N layers, which is caused by the spinodal decomposition of the cubic TiAlN phase. While the thermal emittance slightly increased from 0.134 to 0.154, as the TiN IR reflector maintained its layer structure even up to 1100 °C.

Optimization of a Pb-free all-perovskite tandem solar cell with 30.85% efficiency

We present simulation results obtained with the SCAPS-1D simulation package of a lead-free all-perovskite tandem solar cell. The top and bottom subcells, consisting of MAGeI3, and FASnI3, respectively, were optimized individually by varying material properties such as thickness, electron affinity, and capture cross-section. These standalone optimized subcells are then utilized for the tandem structure. The optimal tandem cell thickness was determined based on short circuit current density (JSC) matching of the standalone subcells by varying the subcells’ thickness. A matching JSC of 14.70 mA/cm2 was obtained for the top and bottom subcell thickness of 983 nm and 1600 nm, respectively. At this current matching condition, the simulation show that a tandem cell would yield a high open-circuit voltage (VOC) of 2.63 V, resulting in an efficiency of 30.85%, significantly higher than that of each subcell.

A Robotic Milling System Based on 3D Point Cloud

Industrial robots have advantages in the processing of large-scale components in the aerospace industry. Compared to CNC machine tools, robot arms are cheaper and easier to deploy. However, due to the poor consistency of incoming materials, large-scale and lightweight components make it difficult to automate robotic machining. In addition, the stiffness of the tandem structure is quite low. Therefore, the stability of the milling process is always a concern. In this paper, the robotic milling research is carried out for the welding pre-processing technology of large-scale components. In order to realize the automatic production of low-conformity parts, the on-site measurement–planning–processing method is adopted with the laser profiler. On the one hand, the laser profiler hand–eye calibration method is optimized to improve the measurement accuracy. On the other hand, the stiffness of the robot’s processing posture is optimized, combined with the angle of the fixture turntable. Finally, the experiment shows the feasibility of the on-site measurement–planning–processing method and verifies the correctness of the stiffness model.

Exceptional Photocatalytic Activities of rGO Modified (B,N) Co-Doped WO3 , Coupled with CdSe QDs for One Photon Z-Scheme System: A Joint Experimental and DFT Study.

Artificial Z‐scheme, a tandem structure with two‐step excitation process, has gained significant attention in energy production and environmental remediation. By effectively connecting and matching the band‐gaps of two different photosystems, it is significant to utilize more photons for excellent photoactivity. Herein, a novel one‐photon (same energy‐two‐photon) Z‐scheme system is constructed between rGO modified boron‐nitrogen co‐doped‐WO3, and coupled CdSe quantum dots‐(QDs). The coctalyst‐0.5%Rh x Cr2O3(0.5RCr) modified amount‐optimized sample 6%CdSe/1%rGO3%BN‐WO3 revealed an unprecedented visible‐light driven overall‐water‐splitting to produce ≈51 µmol h−1 g−1 H2 and 25.5 µmol h−1 g−1 O2, and it remained unchanged for 5 runs in 30 h. This superior performance is ascribed to the one‐photon Z‐scheme, which simultaneously stimulates a two photocatalysts system, and enhanced charge separation as revealed by various spectroscopy techniques. The density‐functional theory is further utilized to understand the origin of this performance enhancement. This work provides a feasible strategy for constructing an efficient one‐photon Z‐scheme for practical applications.

Minimizing Open‐Circuit Voltage Loss in Perovskite/Si Tandem Solar Cells via Exploring the Synergic Effect of Cations and Anions

In article number 2100119, Zeguo Tang, Yongzhe Zhang, and co-workers discuss how adopting a perovskite/Si tandem solar cell structure is an effective approach to break the S–Q limit of single-junction solar cells. Minimizing the open-circuit voltage loss of the top perovskite solar cell is critical to achieving a high efficiency of the tandem cell because the open-circuit voltage of the bottom Si cell is fixed, relatively, and the addition of MACl plays such a role.

Optimisation of four-terminal GaAs//Si tandem solar cells using numerical simulation

III–V//crystalline-silicon (c-Si) multi-junction solar cells exhibit great potential in the development of high-efficiency and cost-effective photovoltaic devices. Numerical simulation tools are fast and convenient approaches to optimise cell operation, compared to optimisation techniques involving costly extending experiments. In this study, optimisation of a four-terminal GaAs//c-Si tandem structure was modelled through automat for simulation of heterostructures (AFORS-HET) simulation. Various window layers, including AlGaAs, InGaP, AlInP, and AlGaInP layers, and absorber thicknesses were examined and compared to obtain the optimal light collection for the GaAs top cell. In addition, the absorber thicknesses and defect densities of the c-Si bottom cells were used to obtain optimal light absorption. The tandem operation was modelled by illuminating the top and bottom cells separately, with different spectral irradiance sources. The results indicated that the tandem structure with a 1.5 μm thick GaAs top and an AlGaAs window layer, in combination with 200-μm thick c-Si bottom cells, showed an optimal efficiency of 32.57%. These simulation results can be used as baselines for strictly experimental processes in the future. The cell operational mechanisms under these variations are detailed herein.

Design of white tandem organic light‐emitting diodes for full‐color microdisplay with high current efficiency and high color gamut

Microdisplays based on organic light-emitting diodes (OLEDs) have a small form factor, and this can be a great advantage when applied to augmented reality and virtual reality devices. In addition, a high-resolution microdisplay of 3000 ppi or more can be achieved when applying a white OLED structure and a color filter. However, low luminance is the weakness of an OLED-based microdisplay as compared with other microdisplay technologies. By applying a tandem structure consisting of two separate emission layers, the efficiency of the OLED device is increased, and higher luminance can be achieved. The efficiency and white spectrum of the OLED device are affected by the position of the emitting layer in the tandem structure and calculated via optical simulation. Each white OLED device with optimized efficiency is fabricated according to the position of the emitting layer, and red, green, and blue spectrum and efficiency are confirmed after passing through color filters. The optimized white OLED device with color filters reaches 97.8% of the National Television Standards Committee standard.

Manage the environmental risks of perovskites

Manage the environmental risks of perovskites

Steering electron transfer using interface engineering on front-illuminated robust BiVO4 photoanodes

Front solar illumination on BiVO 4 is becoming important to design tandem structures in photoelectrochemical (PEC) water splitting. However, the interfacial recombination of BiVO 4 /substrate (e.g. FTO) is more serious than the bulk/surface recombination, which influences the electron transfer to the back side for hydrogen reaction. The BiVO 4 electrode therefore requires back illumination to obtain the best photoresponse. In this context, we proposed a universal strategy by applying a PdO layer functionalized SnO 2 interface as a useful electron transport layer to strikingly reduce the interface recombination. A trace amount of Pd was doped in the bulk BiVO 4 to modify the electronic structure by inducing a stronger dopant-host interaction than that of the surface-modified electrode and homogenous doping. The BiVO 4 /PdO electrodes exhibited similar PEC performance under both front and back illumination. The champion cocatalyst-free photoanode showed a record-high photocurrent of 4.90 mA cm −2 at 1.23 V RHE with a low onset potential of 0.15 V RHE in borate buffer electrolyte under AM 1.5 G front-illumination, accompanying with solar conversion efficiency of 1.72% at 0.6 V RHE . Equally importantly, a sustained long-term photostability over 80 h was achieved, which is the best performance and stability reported among the cocatalyst-free BiVO 4 photoelectrodes from front illumination. This work will open a new avenue for high-stability-performance photoelectrode design. The interfacial recombination of BiVO 4 /substrate is a serious issue for front-illuminated BiVO 4 on designing tandem structures with a wireless configuration. An effective PdO deposition strategy as gate interlayer is proposed to functionalize substrate and boost the electron transfer to the back side for hydrogen reaction. A trace amount of Pd doped into BiVO 4 increases the charge transfer rate of the bulk material. The electrode exhibits similar PEC performances under both front and back illumination, accomanying with long-term photostability over 80 h under solar front illumination. • Interface engineering by appplying PdO layer between the BiVO 4 /substrate is induced for steering electron transfer. • Cathodic photocorrosion is reduced for stabilizing front-illuminated BiVO 4 photoanode. • Effective carrier management is well controlled for reverse gradient Pd doping in BiVO 4 with increased oxygen vacancies. • A photocurrent of 4.9 mA cm −2 at 1.23 V RHE and a long-term photodurability over 80 h are obtained for cocatalyst-free BiVO 4 .

Interlayer Microstructure Analysis of the Transition Zone in the Silicon/Perovskite Tandem Solar Cell

The aim of the paper was to determine the morphology of the layers and the microstructure of the transition zone present in the proposed tandem solar structure. The bottom-silicon solar cell plays a double role: first as a highly porous non-reflecting material, and second as a scaffold for top-perovskite cell. In the presented solution, the use of a porous layer made of (e.g., TiO2) is excluded in favor of chemically etched wires on the silicon surface. The porous layer of silicon consists of nano- and microwires etched with metal assisted etching (MAE). The perovskite layer is introduced by a two-step chemical method into the spaces between the wires to fully fill them and intentionally form an additional capping layer at the same time. To examine the structure made in this way, advanced microscopic methods were used including scanning electron microscopy (SEM), transmission electron microscopy (TEM), and scanning transmission electron microscopy (STEM), also in high resolution.

Optimization of various terminal topologies of bifacial perovskite/FeSi2 tandem solar cell

Although perovskite (PVK) and bifacial solar cell technologies have gained a rapid emergence in recent years, integration of PVK with low-cost high-efficiency subcell in a bifacial tandem structure is still an area of huge interest. In this work, the potential of FeSi2 thin film solar cell to be used as bottom subcell in a PVK based bifacial tandem cell structure is explored. We use self-consistent electrical-optical model to investigate various terminal topologies of PVK/FeSi2 bifacial tandem solar cell. In particular, we compare a novel three terminal four junction (3T-4J) tandem configuration termed as twin (or double) tandem cell with conventional monolithic two terminal (2T) and mechanically stacked four terminal (4T) bifacial tandem structures having two junction (2J) configuration. We show that the optimal thickness of PVK in 2T-2J tandem configuration is strongly dependent upon magnitude of albedo due to the current-matching constraint between the subcells, whereas both 4T-2J and 3T-4J tandem cells can perform optimally for a broad range of albedo. At optimal cell design, all tandem structures could exhibit efficiency >27.5% at average Earth albedo of ∼30%. Lastly, the results presented in this work provide a complete design space for optimal cell operations and would be beneficial for the development of low-cost high-efficiency PVK based bifacial tandem solar cell.

Special Issue on the 40th Anniversary of University of Macau

Special Issue on the 40th Anniversary of University of Macau

Synthesis of hierarchical tandem double Z-scheme heterojunctions for robust photocatalytic H2 generation

The design of advanced structures for semiconductor photocatalysts is one of the most tremendous approaches to stimulate their conversion performance from solar energy to chemical energy. Nonetheless, it is challenging to harvest the full solar spectrum in semiconductor photocatalysts for excessive activity. Herein, a hierarchical CuCo2O4/graphdiyne/CuO nanocages (CCOGC NCs) tandem heterojunction was once effectively synthesized by means of liquid–liquid interface method for the first time and a facile calcination method. The graphdiyne nanosheets (GDY NSs) not only function as a cost-effective cocatalyst but also act as a bridge to connect two light-harvesting semiconductors into a tandem heterojunction where the CuCo2O4 (CCO) NCs and CuO Quantum dots (QDs) absorb visible light on both sides efficiently, coupling with the GDY NSs into a double Z-scheme photocatalyst system. Benefiting from the novel hierarchical tandem nanocages structure, the optimized CCOGC NCs photocatalyst manifests high activity under visible light irradiation with the hydrogen (H2) generation rate of 9617 µmol h−1 g−1, which is much enhanced compared with those of the CCO NCs and CCO/GDY NCs (CCOG NCs), as well CCO/CuO (CCOC NCs).

A study on the influence of the albedo spectrum on the bifacial GaAs/c-Si heterojunction tandem solar cell using computer modelling

Recently, III-V/c-Si heterojunction (c-Si HJ) tandem solar cells received considerable attention owing to their high conversion efficiency. In a tandem configuration, current matching has a significant impact on conversion efficiency. Specifically, in the two-terminal tandem structure, the sub-cell with the lowest current density (Jsc) dominates the Jsc of the tandem cell, which in turn, dominates the overall conversion efficiency of the tandem device. Meanwhile, in a four-terminal tandem structure, although the current matching condition is not mandatory, an efficient light distribution is necessary to achieve high efficiency in each sub-cell, which in turn results in a high efficiency of the tandem cell. Herein, we propose two- and four-terminal GaAs/c-Si HJ tandem solar cells using effective albedo reflections (RA) to overcome the aforementioned limitations. As RA increased, the current density of the c-Si HJ solar cells increased from 3.07 mA/cm2 (RA = 10%) to 39.90 mA/cm2 (RA = 100%) on the rear side of the cell, thereby, overcaming the existing current density limit. In addition, we investigated the tandem structures via simulation to provide a practical direction for achieving high efficiency. Finally, normalised outputs of 40.00% and 40.31% were achieved for the two-terminal and four-terminal GaAs/c-Si HJ bifacial tandem solar cells, respectively, with a real-life albedo from common ground surfaces, such as sand.

Durable and efficient photoelectrochemical water splitting using TiO2 and 3C–SiC single crystals in a tandem structure

Hydrogen can be generated by the photolysis of water with semiconductors as photocatalysts. The most important characteristics of water splitting are its durability and efficiency. Furthermore, TiO 2 and 3C–SiC are durable photocatalysts. Because of their different band gaps and conductivity types, a tandem structure combined with these materials functions as an efficient and durable solar water splitting system. It was observed that the photocurrent from the tandem structure was higher at low pH, as noted by the pH dependence of the photocurrent at the TiO 2 photoanode. The photocurrent from the tandem structure had a light intensity dependence similar to the photocurrent from the TiO 2 photoanode. Therefore, the performance of the tandem structure appears to be limited by the photocurrents from the TiO 2 photoanode. We obtained a maximum applied bias photon-to-current conversion efficiency of approximately 0.74% from the tandem structure with no additional bias applied. We also confirmed the presence of a stable photocurrent from the tandem structure for over ~100 days. •The pH dependence and the irradiation light intensity dependence of TiO 2 , 3C–SiC single crystals and the tandem structure combined were characterized. •The lower the pH, the higher the irradiation light intensity, the better the performance of TiO 2 , 3C–SiC single crystals and the tandem structure. •The measured value of the hydrogen generation is 85% of the calculated value which means that hydrogen is almost completely generated in the actual hydrogen and oxygen generation experiment. •The tandem structure shows a 100 days' long-term durability which is pretty longer than most of the photoelectrodes and photocatalysts.

Network Anomaly Traffic Detection Method Based on Multi-SAE and LSTM

For the purpose of faster and more accurate anomalous traffic detection with increasing classes of data traffic in the network, this paper proposes a new anomalous traffic detection method based on stacked auto-encoders and a long short-term memory network model. The method uses Multi-SAE to extract the effective features of sequential traffic, which is obtained by concatenating multiple stacked auto-encoders, and a long short-term memory network to extract the temporal structure of the effective features, with the Multi-SAE and the long short-term memory network in a back-and-forth tandem structure. To further improve the efficiency of the detection, redundant MAC addresses are also removed in the pre-processing. From the experimental results, this paper achieves effective detection of twenty types of data traffic with an accuracy rate of 98.25%, which is higher than that of the same category of research by nearly 2 percentage points, and the parameters of precision, recall and f1-score also reach over 96%, improving the detection results.