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AZO@Ag nanowire@AZO (AAA) composite stretchable transparent electrode enables full-solution-processed semi-transparent intrinsically stretchable OPV achieving record 10.90% PCE, with excellent mechanical robustness against stretch-release cycles.

Highly conductive, durable, and breathable metal-coated textiles are critical building block materials for future wearable electronics. In order to enhance the metal adhesion on the textile surface, existing solution-based approaches to preparing these materials require time-consuming presynthesis and/or premodification processes, typically in the order of tens of minutes to hours, on textiles prior to metal plating. Herein, we report a UV-induced rapid polymer-assisted metal deposition (r-PAMD) that offers a destructive-treatment-free process to deposit highly conductive metals on a wide variety of textile materials, including cotton, polyester, nylon, Kevlar, glass fiber, and carbon cloth. In comparison to the state of the arts, r-PAMD significantly shortens the modification time to several minutes and is compatible with the roll-to-roll fabrication manner. Moreover, the deposited metals show outstanding adhesion, which withstands rigorous flexing, abrasion, and machine washing tests. We demonstrate that these metal-coated textiles are suitable for applications in two vastly different fields, being wearable and washable sensors, and lithium batteries.

The addition of small seeding particles into a supersaturated solution is one among the most effective approaches to obtain high-quality semiconductor materials via increased crystallization rates. However, limited study is conducted on this approach for the fabrication of perovskite solar cells. Here, a new strategy-"heterogenous seeding-induced crystallization (hetero-SiC)" to assist the growth of FAPbI

Summary With amazing progress in the state-of-the-art perovskite solar cells (PSCs) fabricated by laboratory-scale spin-coating methods, upscaling the PSCs via printing friendly techniques is becoming more and more important toward the future deployment of large-scale and stable perovskite modules. Here, we demonstrate the room-temperature meniscus coating of high-quality perovskite films incorporated with a multifunctional sulfobetaine-based zwitterionic surfactant. Systematic in situ studies uncover the perovskite crystallization pathway and emphasize the surfactant’s synergistic role in film construction, crystallization kinetics modulation, defect passivation, and moisture barrier protection. This strategy is applicable across perovskite compositions and device architectures with the enhanced power conversion efficiencies up to 22%. Upscaling the device area to 0.8 cm2 has negligible deterioration in the performance. This represents one of the highest records for the upscaling coated PSCs, not limited in room-temperature coated PSCs. In addition, this approach significantly improves the stability of perovskite films and devices under different aging conditions.

Perovskite solar cells (PSCs) are promising technology for flexible photovoltaic applications because of the low cost and good flexibility of the halide perovskite materials. Nevertheless, the use of transparent conductive oxides (TCOs) and noble metals (e.g., Au and Ag) as PSC electrodes is very costly, and TCOs are too brittle for flexible applications. How to fabricate flexible PSCs (FPSCs) with cost-effective and soft electrode materials remains to be a big challenge. Herein, we report the first study of FPSCs using low-cost Cu electrodes. Both the transparent bottom electrode and the opaque top electrode are fabricated with Cu. FPSCs made with such Cu electrodes acquire a champion efficiency of 13.58% (Jsc of 17.79 mA cm-2, Voc of 1.031 V, and FF of 74.07%), which retains over 90% after 1000 cycles of bending at a small radius of curvature of 5 mm. The device shows negligible changes in Voc and FF after storage for 10 weeks without encapsulation.

Monolithic integration of nanostructured metalenses with broadband light transmission and good charge transport can simultaneously enhance the sensitivity, speed, and efficiency of photodetectors. The realization of built-in broadband metalenses in perovskite photodetectors, however, has been largely challenged by the limited choice of materials and the difficulty in nanofabrication. Here a new type of broadband-transmitting built-in TiO

From a base material of conductive polymer (poly-(3,4-ethylenedioxythiophene):poly(styrenesulfonate), PEDOT:PSS), a flexible and high-conductivity (as low as 45 Ω/sq) transparent electrode was fabricated on polydimethylsiloxane elastomer by an acid treatment and transfer process. Combined with the D-sorbitol-doped PEDOT:PSS electric glue, we successfully demonstrated a vacuum-free and ambient lamination fabrication process for semi-transparent perovskite solar cells using triple cation Cs005(MA017FA083)095Pb(I083Br017)3 perovskite. By this manufacturing-friendly lamination process, we fabricated semi-transparent perovskite solar cell devices with power conversion efficiencies up to 16.4% and variable transparencies.

With the direct contact ice production technique, ice blockage around the injector, large refrigerant charge and difficulty in separating the refrigerant from water always occur. In order to overcome these problems, the combined of a spiral jet (SPJT) and a horizontal PVC pipe is developed to achieve continuous ice production, and RC318 is selected as the refrigerant. The effect of rotational speed of the compressor on water temperature decrement, ice production rate, ice packing factor (IPF), COP and coefficient of ice producing performance (CIPP) is investigated in this study. The results show that as the rotational speed increases, a faster drop of water temperature and a higher ice production rate are obtained, which result in higher IPF under fixed duration. However, an increase in rotational speed leads to a decrease in COP. The maximum CIPP is 6.64×10-3 kg/kJ at rotational speed of 2700rpm. Moreover, at high rotational speed of 2820rpm, the cooling capacity becomes worse at the later stage of ice production process. Conclusively, the rotational speed of 2700rpm is considered as the optimal working condition.

α-Formamidinium lead triiodide (α-FAPbI

Epitaxial growth gives the highest-quality crystalline semiconductor thin films for optoelectronic devices. Here, a universal solution-processed bottom-up quasi-epitaxial growth of highly oriented α-formamidinium lead triiodide (α-FAPbI3 ) perovskite film via a two-step method is reported, in which the crystal orientation of α-FAPbI3 film is precisely controlled through the synergetic effect of methylammonium chloride and the large-organic cation butylammonium bromide. In situ GIWAXS visualizes the BA-related intermediate phase formation at the bottom of film, which serves as a guiding template for the bottom-up quasi-epitaxial growth in the subsequent annealing process. The template-guided epitaxially grown BAFAMA perovskite film exhibits increased crystallinity, preferred crystallographic orientation, and reduced defects. Moreover, the BAFAMA perovskite solar cells demonstrate decent stability, maintaining 95% of their initial power conversion efficiency after 2600 h ambient storage, and 4-time operation condition lifetime enhancement.

For the direct contact ice slurry production system, the obstacles of ice blockage in the nozzle, enormous refrigerant charge, and refrigerant-water separation restrict its commercial application. In this paper, a novel direct contact ice slurry production system is proposed to overcome these obstacles. In this novel system, the horizontal PVC pipe with the spiral nozzle is designed as a direct contact ice slurry generator to avoid ice blockage in the nozzle. The two-phase RC318 is utilized as the system refrigerant. In order to investigate the ice production performance of this novel system, the effects of compressor rotational speed, internal water flowrate, and initial system pressure on ice production performance are experimentally studied, and a lump model is established. The results show that the ice production performance is mainly affected by the compressor rotational speed, but scarcely affected by the internal water flowrate. However, large ice blocks are formed at small internal water flowrate. Besides, the lump model is considered to be able to predict the water temperature. Furthermore, the sinking of the liquid refrigerant exits under the higher initial system pressure, but it can be avoided by reducing the initial system pressure.

Excess PbI2 management is critical to the performance and stability of perovskite solar cells (PSCs). However, typical post treatment method remains the nature of instability induced by the photolysis of PbI2. Herein, by forming robust self-assembled supramolecules ([BMIM]PbI2X5 and [BMIM]PbX3) with 1-butyl-3-methylimidazolium based ionic liquids ([BMIM]X), we report a novel “Ionic Liquid assisted Supramolecular Complex engineering” (ILaSC) approach to effectively modulate the unreacted PbI2. The formation process and mechanism of supramolecules are elucidated. With effective Pb interstitial defects passivation and tensile strain relaxation simultaneously, the ILaSC approach achieves significant enhancements in both PCE (from 21.9% to 23.5%) and device stability (retaining 95% of the initial PCE after 4080 h in ambient dry-air storage, and 80% after 1400 h continuous light illumination). The generality of the supramolecular complex engineering methodology in broader ionic salt systems is further demonstrated, representing a new direction towards highly stable and efficient PSCs.

Solution-processed solar cells are appealing because of the low manufacturing cost, the good compatibility with flexible substrates, and the ease of large-scale fabrication. Whereas solution-processable active materials have been widely adopted for the fabrication of organic, dye-sensitized, and perovskite solar cells, vacuum-deposited transparent conducting oxides (TCOs) such as indium tin oxide, fluorine-doped tin oxide, and aluminum-doped tin oxide are still the most frequently used transparent electrodes (TEs) for solar cells. These TCOs not only significantly increase the manufacturing cost of the device, but also are too brittle for future flexible and wearable applications. Therefore, developing solution-processed TEs for solar cells is of great interest. This paper provides a detailed discussion on the recent development of solution-processed TEs, including the chemical synthesis of the electrode materials, the solution-based technologies for the electrode fabrication, the optical and electrical properties of the solution-processed TEs, and their applications on solar cells.

In this work, we report systematic studies on improving the optical and electrical properties of four-terminal perovskite/c-Si tandem solar cells. Light harvesting power of the device is significantly enhanced due to the complementary absorption spectra of the perovskite and c-Si absorber materials. To obtain high power conversion efficiency (PCE) for the device, careful engineering of optoelectronic properties of the devices are accomplished through: 1. Oxygen annealing treatment for reducing defect density of perovskite materials; 2. Optical engineering of the transparent electrode (MoO3/Au/MoO3) to obtain high transmission at long wavelengths for the tandem solar cell applications; and 3. Enhancement of light harvesting power achieved by using the novel biomimicking elastomeric petals as the light trapping layer. The individual perovskite solar cell (PSC) with MoO3/Au/MoO3 electrode with or without light trapping layer yields an average PCE of 16.6% and 16.0% respectively. By combining c-Si bottom cell with perovskite top cell mechanically, an overall PCE of 22.4% is achieved for the averaged value, which is a promising result for future development of perovskite based tandem solar cells.

Monolithic integration of nanostructured metalenses with broadband light transmission and good charge transport can simultaneously enhance the sensitivity, speed, and efficiency of photodetectors. The realization of built-in broadband metalenses in perovskite photodetectors, however, has been largely challenged by the limited choice of materials and the difficulty in nanofabrication. Here a new type of broadband-transmitting built-in TiO2 metalens (meta-TiO2 ) is devised, which is readily fabricated by one-step and lithograph-free glancing angle deposition. The meta-TiO2 , which comprises of sub-100 nm TiO2 nanopillars randomly spaced with a wide range of sub-wavelength distances in 5-200 nm, shows high transmittance of light in the wavelength range of 400-800 nm. The meta-TiO2 also serves as an efficient electron transporting layer to prevent the exciton recombination and facilitate the photoinduced electron extraction and transport. Replacing the conventional mesoporous TiO2 with the meta-TiO2 comprehensively leads to enhancing the detection speed by three orders of magnitude to a few hundred nanoseconds, improving the responsivity and detectivity by one order of magnitude to 0.5 A W-1 and 1013 Jones, respectively, and extending the linear dynamic range by 50% to 120 dB.

α-Formamidinium lead triiodide (α-FAPbI3 ) represents the state-of-the-art for perovskite solar cells (PSCs) but experiences intrinsic thermally induced tensile strain due to a higher phase-converting temperature, which is a critical instability factor. An in situ crosslinking-enabled strain-regulating crystallization (CSRC) method with trimethylolpropane triacrylate (TMTA) is introduced to precisely regulate the top section of perovskite film where the largest lattice distortion occurs. In CSRC, crosslinking provides in situ perovskite thermal-expansion confinement and strain regulation during the annealing crystallization process, which is proven to be much more effective than the conventional strain-compensation (post-treatment) method. Moreover, CSRC with TMTA successfully achieves multifunctionality simultaneously: the regulation of tensile strain, perovskite defects passivation with an enhanced open-circuit voltage (VOC = 50 mV), and enlarged perovskite grain size. The CSRC approach gives significantly enhanced power conversion efficiency (PCE) of 22.39% in α-FAPbI3 -based PSC versus 20.29% in the control case. More importantly, the control PSCs' instability factor-residual tensile strain-is regulated into compression strain in the CSRC perovskite film through TMTA crosslinking, resulting in not only the best PCE but also outstanding device stability in both long-term storage (over 4000 h with 95% of initial PCE) and light soaking (1248 h with 80% of initial PCE) conditions.

Most existing room temperature magnetic refrigeration (MR) prototypes are based on the concept of an active magnetic regenerator (AMR). However, for these MR prototypes, three obstacles, i.e. theoretical limit of the MR thermodynamic cycle, low operating frequency, and large irreversible loss during heat regeneration, limit the enhancement of their temperature span and cooling capacity, and further restrict their commercial application. In this paper, the solutions to these obstacles are reviewed from the perspectives of MR thermodynamic cycles and heat transfer enhancement during heat regeneration. With respect to MR cycles, the future trend is likely to be fully solid-state MR cycle and multi-caloric refrigeration cycle. With regard to heat transfer enhancement, the three methods exhibit good practical prospects, namely using liquid metals or nanofluids as the heat transfer fluid, shaping a magnetocaloric material (MCM) into an enhanced heat transfer structure, and inserting materials with high thermal conductivity in the MCM. Moreover, room-temperature MR applications in the cold-storage device, heat pump and electric vehicle air conditioning are reviewed. Small cooling capacity devices are the primary application targets of room-temperature MR, such as the wine cooler, domestic dehumidifier, and portable personal air conditioning.

A low-cost biomimetic haze film (BHF) is fabricated by one-step replica molding of the petal texture of yellow roses with polydimethylsiloxane (PDMS). The BHF possesses very high haze transmission (75%) and ultrahigh diffusion transmittance (97%), superior anti-reflection ability, remarkable enhancement of light absorption at small incidence angles, and superb resistance to strong acids. When attached on top of the glass side of photovoltaic cells, the BHF significantly elongates the photon pathway in the active layer and enhances the light harvesting of the solar devices. As a result, the power conversion efficiency of Si solar cells, organic solar cells (OSCs) and perovskite solar cells (PSCs) is respectively improved remarkably by 6.8%, 10% and 15%. In addition, >65% of the photocurrent is maintained even at an extremely small light incidence angle (10°), which equals more than 2.7 times the efficiency enhancement of the solar cell without the BHF.

Organic and perovskite solar cells are attractive solar technologies that particularly suitable for flexible and wearable applications because of the printing ability and mechanical softness of the active materials. One key challenge in the realization of these potentially low-cost flexible photovoltaic devices is how to print high-quality transparent and opaque electrodes with good flexibility. Transparent electrodes in current photovoltaics are transparent conductive oxides (TCOs), which are fragile to bending. Opaque electrodes, on the other hand, are made of metals that are difficult to print in high quality. Recently, our research group has developed printable TCO-free transparent electrodes and printable metal electrodes, which possess low resistance, high optical properties, good flexibility, and good smoothness. This talk will discuss the materials and fabrication of these electrodes and the applications on flexible organic, perovskite, and tandem solar cells.

As an alternative to the vapor-compression technology, magnetic refrigeration has been an active area of research in recent years. A serious obstacle faced by existing magnetic refrigeration prototypes is the use of a heat-transfer fluid, which may result in high irreversible losses, large pressure drops and complex fluid circuits. Solid-state magnetic refrigeration has been investigated as a potential solution. For our previously proposed solid-state micro-unit regeneration magnetic refrigerator, the special three-dimensional structure design allows the heat to be regenerated at a small temperature difference. It is note-worthy that a three-dimensional numerical simulation is necessary for analysing the internal heat transfer characteristic and revealing the operation parameters matching rule of micro-unit regeneration cycle. Therefore, in this work a three-dimensional solid-state magnetic refrigerator based on micro-unit regeneration cycle and Peltier elements is modelled in detail. Multiple micro Peltier (9506-063-022M) modules are coupled with a system to enhance the heat regeneration between the magnetocaloric material lattices. The reliability of the model, in parts and in whole, is verified by experimental data. The heat transfer process and performance characteristics are carefully compared and discussed for several configurations, including the system with/without Peltier elements, two types of lattice heat-transfer structures, different Peltier’s input voltages, and different required times for rotation per lattice. The results show that a larger temperature span and higher frequency are obtained when coupled with Peltier elements. Meanwhile, the parallel-plate heat transfer structure of the magnetocaloric material lattice further improves the performance of the system. The optimal system performance is simultaneously determined by the input voltage and rotating speed. Using gadolinium as a magnetocaloric material and in the case of a 0.7 T applied magnetic field, a maximum temperature span of 32 K, an optimal coefficient of performance of 5.45, and a maximum specific cooling power of 252.5 W/kg can be achieved in such a fully solid-state micro-unit regeneration magnetic refrigeration system. The simulation results can serve as guidelines for solid-state magnetic refrigerator design and optimisation.

This paper presents a composite kernel method (MWASCK) based on multiscale weighted adjacent superpixels (ASs) to classify hyperspectral image (HSI). The MWASCK adequately exploits spatial-spectral features of weighted adjacent superpixels to guarantee that more accurate spectral features can be extracted. Firstly, we use a superpixel segmentation algorithm to divide HSI into multiple superpixels. Secondly, the similarities between each target superpixel and its ASs are calculated to construct the spatial features. Finally, a weighted AS-based composite kernel (WASCK) method for HSI classification is proposed. In order to avoid seeking for the optimal superpixel scale and fuse the multiscale spatial features, the MWASCK method uses multiscale weighted superpixel neighbor information. Experiments from two real HSIs indicate that superior performance of the WASCK and MWASCK methods compared with some popular classification methods.

Flexible and wearable electronics is one major technology after smartphones. It shows remarkable application potential in displays and informatics, robotics, sports, energy harvesting and storage, and medicine. As an indispensable part and the cornerstone of these devices, soft metal electrodes (SMEs) are of great significance. Compared with conventional physical processes such as vacuum thermal deposition and sputtering, chemical approaches for preparing SMEs show significant advantages in terms of scalability, low-cost, and compatibility with the soft materials and substrates used for the devices. This review article provides a detailed overview on how to chemically fabricate SMEs, including the material preparation, fabrication technologies, methods to characterize their key properties, and representative studies on different wearable applications.

Printing of metal bottom back electrodes of flexible organic solar cells (FOSCs) at low temperature is of great significance to realize the full-solution fabrication technology. However, this has been difficult to achieve because often the interfacial properties of those printed electrodes, including conductivity, roughness, work function, optical and mechanical flexibility, cannot meet the device requirement at the same time. In this work, we fabricate printed Ag and Cu bottom back cathodes by a low-temperature solution technique named polymer-assisted metal deposition (PAMD) on flexible PET substrates. Branched polyethylenimine (PEI) and ZnO thin films are used as the interface modification layers (IMLs) of these cathodes. Detailed experimental studies on the electrical, mechanical, and morphological properties, and simulation study on the optical properties of these IMLs are carried out to understand and optimize the interface of printed cathodes. We demonstrate that the highest power conversion efficiency over 3.0% can be achieved from a full-solution processed OFSC with the device structure being PAMD-Ag/PEI/P3HT:PC61BM/PH1000. This device also acquires remarkable stability upon repeating bending tests.

Photoreactive and metal-platable copolymer inks are reported for the first time to allow high-throughput printing of high-performance flexible electrodes at room temperature. This new copolymer ink accommodates various types of printing technologies, such as soft lithography molding, screen printing, and inkjet printing. Electronic devices including resistors, sensors, solar cells, and thin-film transistors fabricated with these printed electrodes show excellent electrical performance and mechanical flexibility.

Semitransparent perovskite solar cells (st-PSCs) have received remarkable interest in recent years because of their great potential in applications for solar window, tandem solar cells, and flexible photovoltaics. However, all reported st-PSCs require expensive transparent conducting oxides (TCOs) or metal-based thin films made by vacuum deposition, which is not cost effective for large-scale fabrication: the cost of TCOs is estimated to occupy ≈75% of the manufacturing cost of PSCs. To address this critical challenge, this study reports a low-temperature and vacuum-free strategy for the fabrication of highly efficient TCO-free st-PSCs. The TCO-free st-PSC on glass exhibits 13.9% power conversion efficiency (PCE), and the four-terminal tandem cell made with the st-PSC top cell and c-Si bottom cell shows an overall PCE of 19.2%. Due to the low processing temperature, the fabrication of flexible st-PSCs is demonstrated on polyethylene terephthalate and polyimide, which show excellent stability under repeated bending or even crumbing.

Full-solution-processed flexible organic solar cells (OSCs) are fabricated using low-cost and high-quality printable Cu electrodes, which achieve a power conversion efficiency as high as 2.77% and show remarkable stability upon 1000 bending cycles. This device performance is thought to be the best among all full-solution-processed OSCs reported in the literature using the same active materials. This printed Cu electrode is promising for application in roll-to-roll fabrication of flexible OSCs.

Light-trapping nanorelief metal electrodes have been proven to be an effective approach to improve the absorption performance of flexible organic solar cells (FOSCs). These nanorelief electrodes have been made by conventional vacuum deposition techniques, which are difficult to integrate with roll-to-roll fabrication processes. To address this challenge, this paper reports, for the first time, the fabrication of highly conductive nanorelief Cu electrodes on the flexible substrates through solution printing and polymer-assisted metal deposition at room temperature in the air. FOSCs made with these printed nanorelief Cu electrodes possess not only much improved power conversion efficiency, by 13.5%, but also significant enhancement in flexibility when compared with those made with flat Cu electrodes. Because of the low material and fabrication cost, these printed nanorelief Cu electrodes show great promise in roll-to-roll fabrication of FOSCs in the future.

We document that media coverage before the IPO day significantly relates to IPO underpricing. The relation is asymmetrical: more media articles are associated with more underpricing when the offer price is revised upwards from the midpoint of the initial filing range, while there is no significant relationship between media coverage and underpricing when the offer price is revised downward. Conditioning on positive price revision, one extra piece of media coverage is associated with about two percentage points greater underpricing. The positive relationship between media coverage and underpricing is stronger when ex ante uncertainty is greater. We fail to find any relation between positive media coverage and IPO firms' long run under-performance. Overall, our findings are consistent with theories of underpricing being driven by the need to compensate investors for information acquisition, but are not consistent with investor sentiment or prospect theory explanations. Moreover, we find that recent stock market returns have significant explanatory power when media attention is omitted from the regressions but lose most or all of their significance when media attention is included, raising new questions in the debate over partial adjustment to public information for IPOs.