Silicon heterojunction back contact solar cells by laser patterning.

Back contact silicon solar cells, valued for their aesthetic appeal by removing grid lines on the sunny side, find applications in buildings, vehicles and aircrafts, enabling self-power generation without compromising appearance1-3. Patterning techniques arrange contacts on the shaded side of the silicon wafer, offering benefits for light incidence as well. However, the patterning process complicates production and causes power loss. Here we employ lasers to streamline back contact solar cell fabrication and enhance power conversion efficiency. Our approach produces the first silicon solar cell to exceed 27% efficiency. Hydrogenated amorphous silicon layers are deposited on the wafer for surface passivation and collection of light-generated carriers. A dense passivating contact, diverging from conventional technology practice, is developed. Pulsed picosecond lasers at different wavelengths are used to create back contact patterns. The developed approach is a streamlined process for producing high-performance back contact silicon solar cells, with a total effective processing time of about one-third that of emerging mainstream technology. To meet terawatt demand, we develop rare indium-less cells at 26.5% efficiency and precious silver-free cells at 26.2% efficiency. The integration of solar solutions in buildings and transportation is poised to expand with these technological advancements.

Preparation and Properties of Nb5+-Doped BCZT-Based Ceramic Thick Films by Scraping Process.

A bottleneck characterized by high strain and low hysteresis has constantly existed in the design process of piezoelectric actuators. In order to solve the problem that actuator materials cannot simultaneously exhibit large strain and low hysteresis under relatively high electric fields, Nb5+-doped 0.975(Ba0.85Ca0.15)[(Zr0.1Ti0.9)0.999Nb0.001]O3-0.025(Bi0.5Na0.5)ZrO3 (BCZTNb0.001-0.025BiNZ) ceramic thick films were prepared by a film scraping process combined with a solid-state twin crystal method, and the influence of sintering temperature was studied systematically. All BCZTNb0.001-0.025BiNZ ceramic thick films sintered at different sintering temperatures have a pure perovskite structure with multiphase coexistence, dense microstructure and typical dielectric relaxation behavior. The conduction mechanism of all samples at high temperatures is dominated by oxygen vacancies confirmed by linear fitting using the Arrhenius law. As the sintering temperature elevates, the grain size increases, inducing the improvement of dielectric, ferroelectric and field-induced strain performance. The 1325 °C sintered BCZTNb0.001-0.025BiNZ ceramic thick film has the lowest hysteresis (1.34%) and relatively large unipolar strain (0.104%) at 60 kV/cm, showing relatively large strain and nearly zero strain hysteresis compared with most previously reported lead-free piezoelectric ceramics and presenting favorable application prospects in the actuator field.

Flexible Tactile Sensors with Gradient Conformal Dome Structures.

The trade-off between high sensitivity and wide detection range remains a challenge for flexible capacitive pressure sensors. Gradient structure can provide continuous deformation and lead to a wide sensing range. However, it simultaneously augments the distance between two electrodes, which diminishes the variation in the relative distance and results in a decreased sensitivity. Herein, a conformal design is introduced into the gradient structure to construct a flexible capacitive pressure sensor. The gradient conformal dome structure is fabricated by a simple reverse dome adsorption process. Taking advantage of the progressive deformation behavior of the gradient dielectric, and the significant improvement of relative distance variation between two electrodes from the conformal design, the sensor achieves a sensitivity of 0.214 kPa-1 in an ultrabroad linear range up to 200 kPa. It maintains high-pressure resolution under the preload of 10 and 100 kPa. Benefiting from the rapid response and excellent repeatability, the sensor can be used for physiological monitor and human motion detection, including arterial pulse, joint bending, and motion state. The gradient conformal design strategy may pave a promising avenue to develop pressure sensors with high sensitivity and wide linear range.

Over 21% Efficient Cesium Lead Triiodide Solar Cell Enabled by Molten Salt Accelerating the Crystallization Processes.

High-quality CsPbI3 with low defect density is indispensable for acquiring excellent photoelectric performance. Meticulous regulation of the CsPbI3 crystal growth processes is both feasible and efficacious in enhancing the quality of perovskite films. In this study, the cesium formate (CsFo) is introduced. On one hand, its low melting point can induce the crystallization processes at a low level of energy consumption. On the other hand, the pseudo-halide anion can participate in the passivation of iodide vacancies, as the formate anion exhibits a relatively higher affinity with iodide vacancies compared to other halides. Consequently, the introduction of CsFo enhances the quality of CsPbI3 thin films by altering the crystallization process and curbing defect formation. As a result, a steady-state output efficiency of 21.23% and an open-circuit voltage (Voc) as high as 1.25 V are achieved, with both parameters ranking among the highest for this type of solar cell.

Fast, variable stiffness-induced braided coiled artificial muscles.

Biomimetic actuation technologies with high muscle strokes, cycle rates, and work capacities are necessary for robotic systems. We present a muscle type that operates based on changes in muscle stiffness caused by volume expansion. This muscle is created by coiling a mechanically strong braid, in which an elastomer hollow tube is adhesively attached inside. We show that the muscle reversibly contracts by 47.3% when driven by an oscillating input air pressure of 120 kilopascals at 10 Hz. It generates a maximum power density of 3.0 W/g and demonstrates a mechanical contractile efficiency of 74%. The muscle's low-pressure operation allowed for portable, thermal pneumatical actuation. Moreover, the muscle demonstrated bipolar actuation, wherein internal pressure leads to muscle length expansion if the initial muscle length is compressed and contraction if the muscle is not compressed. Modeling indicates that muscle expansion significantly alters its stiffness, which causes muscle actuation. We demonstrate the utility of BCMs for fast running and climbing robots.

25.71 %-Efficiency FACsPbI3 Perovskite Solar Cells Enabled by A Thiourea-based Isomer.

Various isomers have been developed to regulate the morphology and reduce defects in state-of-the-art perovskite solar cells (PSCs). To insight the structure-function-effect correlations for the isomerization of thiourea derivatives on the performance of the PSCs, we developed two thiourea derivatives [(3,5-dichlorophenyl)amino]thiourea (AT) and N-(3,5-dichlorophenyl)hydrazinecarbothioamide (HB). Supported by experimental and calculated results, it was found that AT can bind with undercoordinated Pb2+ defect through synergistic interaction between N1 and C=S group with a defect formation energy of 1.818 eV, which is much higher than that from the synergistic interaction between two -NH- groups in HB and perovskite (1.015 eV). Moreover, the stronger interaction between AT and Pb2+ regulates the crystallization process of perovskite film to obtain a high-quality perovskite film with high crystallinity, large grain size, and low defect density. Consequently, the AT-treated FACsPbI3 device engenders an efficiency of 25.71 % (certified as 24.66 %), which is greatly higher than control (23.74 %) and HB-treated FACsPbI3 devices (25.05 %). The resultant device exhibits a remarkable stability for maintaining 91.0 % and 95.2 % of its initial efficiency after aging 2000 h in air condition or tracking at maximum power point for 1000 h, respectively.

Optimizing Crystal Orientation and Defect Mitigation in Antimony Selenide Thin-Film Solar Cells through Buffer Layer Energy Band Adjustment.

Antimony selenide (Sb2Se3) has sparked significant interest in high-efficiency photovoltaic applications due to its advantageous material and optoelectronic properties. In recent years, there has been considerable development in this area. Nonetheless, defects and suboptimal [hk0] crystal orientation expressively limit further device efficiency enhancement. This study used Zinc (Zn) to adjust the interfacial energy band and strengthen carrier transport. For the first time, it is discovered that the diffusion of Zn in the cadmium sulfide (CdS) buffer layer can affect the crystalline orientation of the Sb2Se3 thin films in the superstrate structure. The effect of Zn diffusion on the morphology of Sb2Se3 thin films with CdxZn1-xS buffer layer has been investigated in detail. Additionally, Zn doping promotes forming Sb2Se3 thin films with the desired [hk1] orientation, resulting in denser and larger grain sizes which will eventually regulate the defect density. Finally, based on the energy band structure and high-quality Sb2Se3 thin films, this study achieves a champion power conversion efficiency (PCE) of 8.76%, with a VOC of 458 mV, a JSC of 28.13 mA cm-2, and an FF of 67.85%. Overall, this study explores the growth mechanism of Sb2Se3 thin films, which can lead to further improvements in the efficiency of Sb2Se3 solar cells.

Collaborative Fabrication of High-Quality Perovskite Films for Efficient Solar Modules through Solvent Engineering and Vacuum Flash System.

The vacuum flash solution method has gained widespread recognition in the preparation of perovskite thin films, laying the foundation for the industrialization of perovskite solar cells. However, the low volatility of dimethyl sulfoxide and its weak interaction with formamidine-based perovskites significantly hinder the preparation of cell modules and the further improvement of photovoltaic performance. In this study, we describe an efficient and reproducible method for preparing large-scale, highly uniform formamidinium lead triiodide (FAPbI3) perovskite films. This is achieved by accelerating the vacuum flash rate and leveraging the complex synergism. Specifically, we designed a dual pump system to accelerate the depressurization rate of the vacuum system and compared the quality of perovskite film formed at different depressurization rates. Further, to overcome the limitations posed by DMSO, we substituted N-methylpyrrolidone as the ligand solvent, creating a stable intermediate complex phase. After annealing, it can be transformed into a uniform and pinhole-free FAPbI3 film. Due to the superior quality of these films, the large area perovskite solar module achieved a power conversion efficiency of 22.7% with an active area of 21.4 cm2. Additionally, it obtained an official certified efficiency of 22.1% with an aperture area of 22 cm2, and it demonstrated long-term stability.

Enhancing Adhesion and Reducing Ohmic Contact through Nickel-Silicon Alloy Seed Layer in Electroplating Ni/Cu/Ag.

Due to the lower cost compared to screen-printed silver contacts, the Ni/Cu/Ag contacts formed by plating have been continuously studied as a potential metallization technology for solar cells. To address the adhesion issue of backside grid lines in electroplated n-Tunnel Oxide Passivating Contacts (n-TOPCon) solar cells and reduce ohmic contact, we propose a novel approach of adding a Ni/Si alloy seed layer between the Ni and Si layers. The metal nickel layer is deposited on the backside of the solar cells using electron beam evaporation, and excess nickel is removed by H2SO4:H2O2 etchant under annealing conditions of 300-425 °C to form a seed layer. The adhesion strength increased by more than 0.5 N mm-1 and the contact resistance dropped by 0.5 mΩ cm2 in comparison to the traditional direct plating Ni/Cu/Ag method. This is because the resulting Ni/Si alloy has outstanding electrical conductivity, and the produced Ni/Si alloy has higher adhesion over direct contact between the nickel-silicon interface, as well as enhanced surface roughness. The results showed that at an annealing temperature of 375 °C, the main compound formed was NiSi, with a contact resistance of 1 mΩ cm-2 and a maximum gate line adhesion of 2.7 N mm-1. This method proposes a new technical solution for cost reduction and efficiency improvement of n-TOPCon solar cells.

Effects on Metallization of n+-Poly-Si Layer for N-Type Tunnel Oxide Passivated Contact Solar Cells.

Thin polysilicon (poly-Si)-based passivating contacts can reduce parasitic absorption and the cost of n-TOPCon solar cells. Herein, n+-poly-Si layers with thicknesses of 30~100 nm were fabricated by low-pressure chemical vapor deposition (LPCVD) to create passivating contacts. We investigated the effect of n+-poly-Si layer thickness on the microstructure of the metallization contact formation, passivation, and electronic performance of n-TOPCon solar cells. The thickness of the poly-Si layer significantly affected the passivation of metallization-induced recombination under the metal contact (J0,metal) and the contact resistivity (ρc) of the cells. However, it had a minimal impact on the short-circuit current density (Jsc), which was primarily associated with corroded silver (Ag) at depths of the n+-poly-Si layer exceeding 40 nm. We introduced a thin n+-poly-Si layer with a thickness of 70 nm and a surface concentration of 5 × 1020 atoms/cm3. This layer can meet the requirements for low J0,metal and ρc values, leading to an increase in conversion efficiency of 25.65%. This optimized process of depositing a phosphorus-doped poly-Si layer can be commercially applied in photovoltaics to reduce processing times and lower costs.

High Sensitivity Triboelectric Based Flexible Self-Powered Tactile Sensor with Bionic Fingerprint Ring Structure.

Flexible self-powered tactile sensors, with applications spanning wearable electronics, human-machine interaction, prosthetics, and soft robotics, offer real-time feedback on tactile interactions in diverse environments. Despite advances in their structural development, challenges persist in sensitivity and robustness, particularly when additional functionalities, such as high transparency and stretchability. In this study, we present a novel approach integrating a bionic fingerprint ring structure with a PVDF-HFP/AgNWs composite fiber electrode membrane, fabricated via 3D printing technology and electrospinning, respectively, yielding a triboelectric nanogenerator (TENG)-based self-powered tactile sensor. The sensor demonstrates high sensitivity (5.84 V/kPa in the 0-10 kPa range) and rapid response time (10 ms), attributed to the microring texture on its surface, and exhibits exceptional robustness, maintaining electrical output integrity even after 24,000 cycles of loading. These findings highlight the potential of the microring structures in addressing critical challenges in flexible sensor technology.

Stable Inverted Perovskite Solar Cells with Efficiency over 23.0% via Dual-Layer SnO2 on Perovskite.

Perovskite solar cells (PSCs) have shown great potential for reducing costs and improving power conversion efficiency (PCE). One effective method to achieve the latter is to use an all-inorganic charge transport layer (ICTL). However, traditional methods for crystallizing inorganic layers often result in the formation of a powder instead of a continuous film. To address this issue, we designed a dual-layer inorganic electron transport layer (IETL). This dual-layer structure consists of a layer of SnO2 nanocrystals (SnO2 NCs) deposited via a solution process and a dense SnO2 layer deposited through atomic layer deposition (ALD SnO2) to fill the cracks and gaps between the SnO2 NCs. PSCs having these dual-layer SnO2 ETLs achieved a high efficiency of 23.0%. This efficiency surpasses the recorded performance of ICTLs deposited on the perovskite. Furthermore, the PCE is comparable to that achieved with a C60 ETL. Moreover, the high-density structure of the ALD SnO2 layer inhibits the vertical migration of ions, resulting in improved thermal stability. After continuous heating at 85 °C in 10% humidity for 1000 h, the PCE of the dual-layer SnO2 structure decreased by 18%, whereas that of the C60/BCP structure decreased by 36%. The integration of dual-layer SnO2 into PSCs represents a significant advancement in achieving high-performance, commercially viable inverted monolithic PSCs or tandem solar cells.

Equally Efficient Perovskite Solar Cells and Modules Fabricated via N-Ethyl-2-Pyrrolidone Optimized Vacuum-Flash.

Efficiency reduction in perovskite solar cells (PSCs) during the magnification procedure significantly hampers commercialization. Vacuum-flash (VF) has emerged as a promising method to fabricate PSCs with consistent efficiency across scales. However, the slower solvent removal rate of VF compared to the anti-solvent method leads to perovskite films with buried defects. Thus, this work employs low-toxic Lewis base ligand solvent N-ethyl-2-pyrrolidone (NEP) to improve the nucleation process of perovskite films. NEP, with a mechanism similar to that of N-methyl-2-pyrrolidone in FA-based perovskite formation, enhances the solvent removal speed owing to its lower coordination ability. Based on this strategy, p-i-n PSCs with an optimized interface attain a power conversion efficiency (PCE) of 24.19% on an area of 0.08 cm2. The same nucleation process enables perovskite solar modules (PSMs) to achieve a certified PCE of 23.28% on an aperture area of 22.96 cm2, with a high geometric fill factor of 97%, ensuring nearly identical active area PCE (24%) in PSMs as in PSCs. This strategy highlights the potential of NEP as a ligand solvent choice for the commercialization of PSCs.

(Sb0.5Li0.5)TiO3-Doping Effect and Sintering Condition Tailoring in BaTiO3-Based Ceramics.

(1-x)(Ba0.75Sr0.1Bi0.1)(Ti0.9Zr0.1)O3-x(Sb0.5Li0.5)TiO3 (abbreviated as BSBiTZ-xSLT, x = 0.025, 0.05, 0.075, 0.1) ceramics were prepared via a conventional solid-state sintering method under different sintering temperatures. All BSBiTZ-xSLT ceramics have predominantly perovskite phase structures with the coexistence of tetragonal, rhombohedral and orthogonal phases, and present mainly spherical-like shaped grains relating to a liquid-phase sintering mechanism due to adding SLT and Bi2O3. By adjusting the sintering temperature, all compositions obtain the highest relative density and present densified micro-morphology, and doping SLT tends to promote the growth of grain size and the grain size distribution becomes nonuniform gradually. Due to the addition of heterovalent ions and SLT, typical relaxor ferroelectric characteristic is realized, dielectric performance stability is broadened to ~120 °C with variation less than 10%, and very long and slim hysteresis loops are obtained, which is especially beneficial for energy storage application. All samples show extremely fast discharge performance where the discharge time t0.9 (time for 90% discharge energy density) is less than 160 ns and the largest discharge current occurs at around 30 ns. The 1155 °C sintered BSBiTZ-0.025SLT ceramics exhibit rather large energy storage density, very high energy storage efficiency and excellent pulse charge-discharge performance, providing the possibility to develop novel BT-based dielectric ceramics for pulse energy storage applications.

Design of an actuator with bionic claw hook-suction cup hybrid structure for soft robot.

To improve the adaptability of soft robots to the environment and achieve reliable attachment on various surfaces such as smooth and rough, this study draws inspiration from the collaborative attachment strategy of insects, cats, and other biological claw hooks and foot pads, and designs an actuator with a bionic claw hook-suction cup hybrid structure. The rigid biomimetic pop-up claw hook linkage mechanism is combined with a flexible suction cup of a 'foot pad' to achieve a synergistic adhesion effect between claw hook locking and suction cup adhesion through the deformation control of a soft pneumatic actuator. A pop-up claw hook linkage mechanism based on the principle of cat claw movement was designed, and the attachment mechanism of the biological claw hooks and footpads was analysed. An artificial muscle-spring-reinforced flexible pneumatic actuator (SRFPA) was developed and a kinematic model of the SRFPA was established and analysed using Abaqus. Finally, a prototype of the hybrid actuator was fabricated. The kinematic and mechanical performances of the SRFPA and entire actuator were characterised, and the attachment performance of the hybrid actuator to smooth and rough surfaces was tested. The results indicate that the proposed biomimetic claw hook-suction cup hybrid structure actuator is effective for various types of surface adhesion, object grasping, and robot walking. This study provides new insights for the design of highly adaptable robots and biomimetic attachment devices.

The smallest Schwarzite carbon with only heptagonal carbon rings.

Carbon materials with full sp2-hybridized buckling is a major challenge pervading fundamental nanoscience and nanotechnology research. Carbon atoms that are sp2 hybridized prefer to form hexagonal rings, such as in carbon nanotubes and graphene, which are low-dimensional materials. The incorporation of heptagonal, octagonal, and/or larger rings into a hexagonal sp2 carbon meshwork has been identified as a strategy for assembling three-dimensional (3D) sp2 carbon crystals, and one of the typical representatives are Schwarzite carbons, which possess a negative surface Gaussian curvature as well as unique physical properties. Herein, a 3D Schwarzite carbon consisting of only sp2-buckled heptagonal carbon rings, which is referred to as Hepta-carbon, is proposed based on first-principles calculations. Hepta-carbon is mechanically and thermodynamically stable, and energetically more favourable than experimental graphdiyne, fullerene C20 and most Schwarzite carbons under ambient conditions. Molecular dynamics simulations indicate that Hepta-carbon exhibits high-temperature thermostability up to 1500 K. Band structure and mechanical property simulations indicate that Hepta-carbon is a semi-metallic material with electron conduction and exhibits impressive mechanical properties such as high strength with quasi-isotropy, high incompressibility similar to diamonds, elastic deformation behaviour under uniaxial stress, and high ductility. Hepta-carbon presents a porous network with a low mass density of 1.84 g cm-3 and connected channels with diameters of 3.3-6.1 Å. Theoretical simulations of gas adsorption energy demonstrate that Hepta-carbon can effectively adsorb and stabilize greenhouse gases, including N2O, CO2, CH4, and SF6.

Lead-Free Perovskite Single Crystal Linear Array Detector for High-Resolution X-Ray Imaging.

0D Bi-based 329-type halide perovskite is demonstrated as a promising semiconductor for X-ray detection due to its strong X-ray absorption, superior stability, availability of large single crystals (SCs) and solution processibility at low temperature. However, its low mobility-lifetime product (µτ) limits its further improvement in detection sensitivity. Based on the first-principles calculations, this work designs a new 2D Bi-based 329-type halide perovskite using a mixed-halide-induced structural dimension regulation strategy. By using a continuous supply of a precursor solution, this work successfully grows inch-sized high-quality SCs. These SCs exhibit large µτ product, high resistivity, and low ion migration. The detectors fabricated using the SCs show X-ray detection sensitivity as high as 24,509 µC Gyair -1 cm-2, short response time of 315 µs, low detection limit of 4.3 nGy s-1, and superior stability. These properties are the best among all lead-free perovskite detectors and are comparable to those of the best lead-based perovskite detectors. The linear array detector assembled on the SCs for the first time also shows a high spatial resolution of 10.6 lp mm-1 during X-ray imaging. The high performance combined with superior stability of these new 329-type lead-free halide perovskite SCs is expected to promote a new generation of X-ray detection technologies.

In Situ Synthesized Low-Dimensional Perovskite for >25% Efficiency Stable MA-Free Perovskite Solar Cells.

Developing an additive to effectively regulate the perovskite crystallization kinetics for the optimized optoelectronic properties of perovskite film plays a vital role in obtaining high efficiency and stable perovskite solar cells (PSCs). Herein, a new additive is designed and directly synthesized in perovskite precursor solution by utilizing an addition reaction between but-3-yn-1-amine hydrochloride (BAH) and formamidinium iodide. It is found that its product may control the intermediate precursor phase for regulating perovskite nucleation, leading to advantageous 2D perovskite to induce growth of perovskite along the preferred [001] orientation with not only released lattice strain but also strong interaction with perovskite to passivate its surface defects. By taking advantage of the above synergistic effects, the optimized PSC delivers an efficiency of 25.19% and a high open-circuit voltage (VOC) of 1.22 V. Additionally, the devices demonstrate good stability, remaining over 90% of their initial efficiencies under ambient atmosphere conditions for 60 days, high temperature of 85 °C for 200 h, or maximum power point tracking for 500 h.

Anti-Solvent-Free Preparation for Efficient and Photostable Pure-Iodide Wide-Bandgap Perovskite Solar Cells.

The perovskite/silicon tandem solar cell (TSC) has attracted tremendous attention due to its potential to breakthrough the theoretical efficiency set for single-junction solar cells. However, the perovskite solar cell (PSC) designed as its top component cell suffers from severe photo-induced halide segregation owing to its mixed-halide strategy for achieving desirable wide-bandgap (1.68 eV). Developing pure-iodide wide-bandgap perovskites is a promising route to fabricate photostable perovskite/silicon TSCs. Here, we report efficient and photostable pure-iodide wide-bandgap PSCs made from an anti-solvent-free (ASF) technique. The ASF process is achieved by mixing two precursor solutions, both of which are capable of depositing corresponding perovskite films without involving anti-solvent. The mixed solution finally forms Cs0.3DMA0.2MA0.5PbI3 perovskite film with a bandgap of 1.68 eV. Furthermore, methylammonium chloride additive is applied to enhance the crystallinity and reduce the trap density of perovskite films. As a result, the pure-iodide wide-bandgap PSC delivers efficiency as high as 21.30 % with excellent photostability, the highest for this type of solar cells. The ASF method significantly improves the device reproducibility as compared with devices made from other anti-solvent methods. Our findings provide a novel recipe to prepare efficient and photostable wide-bandgap PSCs.

Defect Passivation Refinement in Perovskite Photovoltaics: Achieving Efficiency over 45% under Low-Light and Low-Temperature Dual Extreme Conditions.

Perovskite photovoltaics have emerged as the most promising candidates for next-generation light-to-electricity technology. However, their practical application still suffers from energy loss induced by intrinsic defects within the perovskite lattice. Here, a refined defect passivation in perovskite films is designed, which shows a multi-interaction mechanism between the perovskite and passivator. Interestingly, a shift of molecular bonding is observed upon cooling down the film, leading to a stronger passivation of iodine/formamidine vacancies. Such mechanism on device under low-light and low-temperature conditions is further leveraged and a record efficiency over 45% with durable ambient stability (T90 > 4000 h) is obtained. The pioneer application of perovskite solar cells in above dual extreme conditions in this work reveals the key principles of designing functional groups for the passivators, and also demonstrates the capability of perovskites for diverse terrestrial energy conversion applications in demanding environments such as polar regions and outer space.