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A pre-embedding mixed A-cation halide strategy is developed to eliminate the residual unstable PbI2 and lattice strain near the buried interface of the perovskite layer for the stability improvement of formamidinium-based perovskite solar cells.

Flexible perovskite solar cells (F-PSCs) hold promise for portable power sources for applications in various fields, such as wearable and portable electronics and lightweight power supply in stratosphere and space applications. To date, it is still a challenge to achieve efficient and stable F-PSCs. Herein, a pre-applied strain on a flexible substrate to release the residual strain of the perovskite layers of the F-PSCs is reported. As a result, the F-PSC based on this strategy yielded a power conversion efficiency (PCE) of up to 18.71%, approaching that of its counterpart based on a glass substrate (20.32%). And it retained 90% of its initial PCE after 300 h under AM 1.5G light illumination with an extrapolated T80 lifetime (the time over which the device efficiency reduces to 80% of its initial value) exceeding 700 h. Furthermore, the PCE remained above 80% of its initial value even after 1500 tension-only bending cycles. The result of this work paves a possible way toward fabricating efficient and stable F-PSCs.

The incorporation of a certain amount of Cl ions into methylammonium lead iodide (MAPbI3) perovskite films and how these incorporated Cl ions affect the structural and electronic properties of these films have been an intensively studied topic. In this study, we comprehensively investigated Cl incorporation in MAPbI3 at the atomic scale by a combined study of scanning tunneling microscopy, X-ray photoelectron spectroscopy, ultraviolet and inverse photoemission spectroscopy, density functional theory and molecular dynamics calculations. At a Cl concentration of 14.8 ± 0.6%, scanning tunneling microscopy images confirm the incorporation of Cl ions on the MAPbI3 surface, which also corresponds to the highest surface stability of MAPbI3 found from the viewpoint of both thermodynamics and kinetics by density functional theory and molecular dynamics calculations. Our results show that the Cl concentration is crucial to the surface bandgap and stability of MAPbI3.

Metal halide perovskite solar cells are an emerging photovoltaic technology already exhibiting great potential. The main challenges at present that hinder the application of perovskite solar cells include scalable fabrication, operational stability, and environmental impact of Pb in Pb-containing perovskite solar cells. Among various scalable coating techniques, modified chemical vapor deposition (CVD) is a promising technology to enable large-area and uniform coating of perovskite layers at a low cost. Modified CVD also offers many other advantages such as being solvent-free, high compatibility with industrial manufacturing, and easy integration with other solar technologies to form tandem cells (or perovskite–perovskite tandem cells). In this review, we present the recent development of perovskite solar cells and modules prepared by modified CVD. We first discuss the differences between modified CVD and solution coating processing. We then summarize the present results from the cost-performance analysis point of view to show the potential of modified CVD for scalable fabrication of perovskite solar cells and modules with low cost. At the end of this review, we outline several future research directions.

The upscaling of perovskite solar cells to module scale and long-term stability have been recognized as the most important challenges for the commercialization of this emerging photovoltaic technology. In a perovskite solar module, each interface within the device contributes to the efficiency and stability of the module. Here, we employed a holistic interface stabilization strategy by modifying all the relevant layers and interfaces, namely the perovskite layer, charge transporting layers and device encapsulation, to improve the efficiency and stability of perovskite solar modules. The treatments were selected for their compatibility with low-temperature scalable processing and the module scribing steps. Our unencapsulated perovskite solar modules achieved a reverse-scan efficiency of 16.6% for a designated area of 22.4 cm2. The encapsulated perovskite solar modules, which show efficiencies similar to the unencapsulated one, retained approximately 86% of the initial performance after continuous operation for 2,000 h under AM1.5G light illumination, which translates into a T90 lifetime (the time over which the device efficiency reduces to 90% of its initial value) of 1,570 h and an estimated T80 lifetime (the time over which the device efficiency reduces to 80% of its initial value) of 2,680 h. The upscaling of layer treatments and processing that afford high efficiency and stability in small-area perovskite solar cells remains challenging. Liu et al. show how the efficiency and stability of perovskite modules can be improved using an integrated approach to interface and layer engineering.

Control of forward and inverse reactions between perovskites and precursor materials is key to attaining high-quality perovskite materials. Many techniques focus on synthesizing nanostructured CsPbX3 materials (e.g., nanowires) via a forward reaction (CsX + PbX2 → CsPbX3). However, low solubility of inorganic perovskites and complex phase transition make it difficult to realize the precise control of composition and length of nanowires using the conventional forward approach. Herein, we report the self-assembly inverse growth of CsPbBr3 micronanowires (MWs) (CsPb2Br5 → CsPbBr3 + PbBr2↑) by controlling phase transition from CsPb2Br5 to CsPbBr3. The two-dimensional (2D) structure of CsPb2Br5 serves as nucleation sites to induce initial CsPbBr3 MW growth. Also, phase transition allows crystal rearrangement and slows down crystal growth, which facilitates the MW growth of CsPbBr3 crystals along the 2D planes of CsPb2Br5. A CsPbBr3 MW photodetector constructed based on the inverse growth shows a high responsivity of 6.44 A W–1 and detectivity of ∼1012 Jones. Large grain size, high crystallinity, and large thickness can effectively alleviate decomposition/degradation of perovskites, which leads to storage stability for over 60 days in humid environment (relative humidity = 45%) and operational stability for over 3000 min under illumination (wavelength = 400 nm, light intensity = 20.06 mW cm–2).

Stretchable electronic textiles are urgently called for due to the emergence of next generation wearable electronics that can undergo various mechanical deformations that exist almost everywhere in our daily lives. In particular, one-dimensional stretchable fibers with excellent electrical conductivity are a promising building block for the construction of stretchable electronic textiles for wearable electronics. However, the reported conductive fibers for stretchable electronics usually have low stretchability and are dark in color, which greatly limit their applications as display devices and colorful electrical textile fabrics. Herein, we report a simple approach toward the fabrication of continuous white conductive fibers with a high stretchability of over 700%, which could offer superfluous deformation capacity. The fiber was fabricated via a dry–wet spinning process using biomass poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3HB4HB) and lab-made electroconductive antimony-doped tin oxide wrapped titanium dioxide nanoparticles (ATO@TiO2 NPs). The system could be mass produced and easily weaved into diverse patterns and shapes. In the resultant composite fiber, the electroconductive ATO@TiO2 NPs are uniformly dispersed in the filler network of P3HB4HB. The fiber revealed impressive reversible mechanical and electrical characteristics within a strain of 420%. Moreover, white stretchable fibers with restorable electroconductive abilities are reported for the first time, thus opening a new opportunity for colorful electrical textile fabrics.

Lead-free double perovskite materials have attracted much interest for optoelectronic applications due to their nontoxicity and high stability. In this work, centimetre-sized Cs2AgBiBr6 single crystals were successfully grown using methylammonium bromide (MABr) as the flux by a top-seeded solution growth (TSSG) method. The low-temperature crystal structure of Cs2AgBiBr6 single crystals was determined and refined. To investigate the interface problems between Cs2AgBiBr6 single crystals and electrodes, the optical band gap, X-ray photoelectron spectroscopy (XPS), and ultraviolet photoemission spectroscopy (UPS) measurements were performed on Cs2AgBiBr6 single crystals. More importantly, we investigated the photodetectors based on Cs2AgBiBr6 single crystals with different contact electrodes (Au, Ag, and Al). It is found that a good Ohmic contact with Ag electrodes enables excellent photo-response behaviors. Furthermore, we studied the photodetectors based on Cs2AgBiBr6 single crystals using Ag electrodes under room and low temperature conditions, which underwent phase transition. Cs2AgBiBr6 single crystal photodetectors show clear differences at room and low temperatures, which is caused by the work function changes of Cs2AgBiBr6 single crystals induced by the reversible phase transition. These attractive properties may enable opportunities to apply emerging double perovskite single-crystalline materials for high-performance optoelectronic devices.

Hybrid chemical vapor deposition (HCVD) has been employed in the fabrication of perovskite solar cells (PSCs) and modules (PSMs), and it shows strong promise for upscalable fabrication. The conventional HCVD process needs a relatively long processing time (e.g., several hours) and the fabricated PSCs often exhibit salient hysteresis, which impedes utilization of this technology for mass production. Herein, we demonstrate a rapid HCVD (RHCVD) fabrication process for PSCs using a rapid thermal process, which not only significantly reduces the deposition time to less than 10 min, but also effectively suppresses hysteresis. This markedly reduced deposition time is comparable to that of solution-coating processes. Furthermore, the shorter processing time inside the furnace reduces the exposure time of the glass/ITO/SnO2 substrates under vacuum, which helps maintain the high quality of the SnO2 electron-transport layer and results in a lower density of gap states. Finally, PSMs with a designated area of 22.4 cm2 fabricated via RHCVD achieved an efficiency of 12.3%, and maintained 90% of the initial value after operation under continuous light illumination for over 800 h.

Perovskite photovoltaic (PV) technology toward commercialization relies on high power conversion efficiency (PCE), long lifetime, and low-toxicity in addition to development of scalable fabrication...

Carbon electrode-based perovskite solar cells (PSCs) with low-cost and long-term stability have been recognized as a competitive candidate toward future practical applications. However, energy leve...

In recent years, the major factors that determine commercialization of perovskite photovoltaic technology have been shifting from solar cell performance to stability, reproducibility, device upscaling and the prevention of lead (Pb) leakage from the module over the device service life. Here we simulate a realistic scenario in which perovskite modules with different encapsulation methods are mechanically damaged by a hail impact (modified FM 44787 standard) and quantitatively measure the Pb leakage rates under a variety of weather conditions. We demonstrate that the encapsulation method based on an epoxy resin reduces the Pb leakage rate by a factor of 375 compared with the encapsulation method based on a glass cover with an ultraviolet-cured resin at the module edges. The greater Pb leakage reduction of the epoxy resin encapsulation is associated with its optimal self-healing characteristics under the operating conditions and with its increased mechanical strength. These findings strongly suggest that perovskite photovoltaic products can be deployed with minimal Pb leakage if appropriate encapsulation is employed. Lead leakage from damaged perovskite solar cells poses a challenge to the deployment of such technology. Here, Jiang, Qiu and co-workers quantify lead leakage caused by a simulated hail impact under a number of weather conditions and show that self-healing encapsulations can effectively reduce it.

The development of scalable deposition methods for stable perovskite layers is a prerequisite for the development and future commercialization of perovskite solar modules. However, there are two major challenges, i.e., scalability and stability. In sharp contrast to a previous report, here we develop a fully vapor based scalable hybrid chemical vapor deposition (HCVD) process for depositing Cs-formamidinium (FA) mixed cation perovskite films, which alleviates the problem encountered when using conventional solution coating of mainly methylammonium lead iodide (MAPbI3). Using our HCVD method, we fabricate perovskite films of Cs0.1FA0.9PbI2.9Br0.1 with enhanced thermal and phase stabilities, by the intimate incorporation of Cs into FA based perovskite films. In addition, the SnO2 electron transport layer (ETL) (prepared by sputter deposition) is found to be damaged during the HCVD process. In combination with precise interface engineering of the SnO2 ETL, we demonstrate relatively large area solar modules with efficiency approaching 10% and with a designated area of 91.8 cm2 fabricated on 10 cm × 10 cm substrates (14 cells in series). On the basis of our preliminary operational stability tests on encapsulated perovskite solar modules, we extrapolated that the T80 lifetime is approximately 500 h (under the light illumination of 1 sun and 25 °C).

Through data analysis and reference of related theories, this paper studies the influence of Pan Hu culture on county economic development from the perspective of economics. It is found that exploiting historical and cultural relics and developing tourism have various effects on economic development. The results show that tourism plays a vital role in economic development, which is reflected in income effect, employment effect, and industrial association effect and so on. Among them, the income effect can directly reflect the impact of tourism on economic development. After research and analysis, we put forward the development countermeasures of combining Pan Hu culture with tourism in Luxi County, and planned the development roadmap of Pan Hu Cultural Site in Luxi County, making Luxi County a cultural town with Pan Hu characteristics. With the development mode of "cultural protection-tourism development-economic growth" complementing each other, we can solve the local employment problem and optimize the industrial structure, thus driving the development of related industries. By studying the in-depth impact of the development of cultural sites in Pan Hu on economic development, this paper provides theoretical guidance for the development of tourism in Yuanshui County, and finally achieves the goal of promoting the integration of urban and rural development in the county.

Metal halide perovskite solar cells have made significant breakthroughs in power conversion efficiency and operational stability in the last decade, thanks to the advancement of perovskite deposition methods. Solution-based methods have been intensively investigated and deliver record efficiencies. On the other hand, vapor deposition-based and assisted methods were less studied in the early years but have received more attention recently due to their great potential toward large-area solar module manufacturing and high batch-to-batch reproducibility. In addition, an in-depth understanding of perovskite crystallization kinetics during the vapor deposition based and assisted process allows increasing perovskite deposition rate and enhancing perovskite quality. In this review, the advances in vapor-based and assisted methods for the fabrication of perovskite solar cells are introduced. The quality of the perovskite layers (i.e., morphology, crystallinity, defect chemistry, carrier lifetime) fabricated by different methods is compared. The limitations of state-of-the-art vapor-deposited perovskite layers are discussed. Finally, insights into the engineering of vapor deposition based and assisted perovskite layers toward efficient and stable perovskite solar cells and modules are provided.

Besides high efficiency, the stability and reproducibility of perovskite solar cells (PSCs) are also key for their commercialization. Herein, we report a simple perovskite formation method to fabricate perovskite films with thickness over 1 μm in ambient condition on the basis of the fast gas−solid reaction of chlorine-incorporated hydrogen lead triiodide and methylamine gas. The resultant thick and smooth chlorine-incorporated perovskite films exhibit full coverage, improved crystallinity, low surface roughness and low thickness variation. The resultant PSCs achieve an average power conversion efficiency of 19.1 ± 0.4% with good reproducibility. Meanwhile, this method enables an active area efficiency of 15.3% for 5 cm × 5 cm solar modules. The un-encapsulated PSCs exhibit an excellent T80 lifetime exceeding 1600 h under continuous operation conditions in dry nitrogen environment.

Organic field-effect transistors (OFETs) are the most fundamental device units in organic electronics. Interface engineering at the semiconductor/dielectric interface is an effective approach for improving device performance, particularly for enhancing charge transport in conducting channels. Here, we report flat-lying molecular monolayers that exhibit good uniformity and high crystallinity at the semiconductor/dielectric interface, deposited through slow thermal evaporation. Transistor devices achieve high carrier mobility up to 2.80 cm2 V–1 s–1, which represents a remarkably improvement in device performance compared with devices that are completely based on fast-evaporated films. Interfacial flat-lying monolayers benefit charge transport by suppressing the polarization of dipoles and narrowing the broadening of trap density of states. Our work provides a promising strategy for enhancing the performance of OFETs by using interfacial flat-lying molecular monolayers.

When transferring photovoltaic technologies from laboratory-scale fabrication to industrial applications, low cost, large area, high throughput, high solar-to-energy power conversion efficiency, long lifetime, and low toxicity are crucial attributes. In recent years, organic–inorganic halide perovskite solar cells have emerged as a promising high-performance, cost-effective solar cell technology. However, most of the best reported efficiencies have been obtained on small active-area devices (∼0.1 cm 2 ). Therefore, development of protocols to industrialize such a technology is of paramount importance. In this article, we review the progress of perovskite solar cells with a particular emphasis on fabrication processes and instrumentation that have scale-up potential. For successful commercialization, the capacity to fabricate large-area modules is essential. Long-term stability is discussed, focusing on lifetime measurement and quantification protocols for commercialization. Cost-performance and life-cycle assessment analysis based on recently reported state-of-the-art perovskite solar cells are discussed. These analyses offer insights regarding required efficiency, module area size, and lifetime, in order for perovskite solar cells to be competitive with existing photovoltaic technologies. Finally, lead toxicity and possible solutions to this issue will be discussed. In the outlook, we outline future research directions based on reported results and trends in the field.

In organic field-effect transistors, the first few molecular layers at the semiconductor/dielectric interface are regarded as the active channel for charge transport; thus, great efforts have been devoted to the modification and optimization of molecular packing at such interfaces. Here, we report organic monolayers with large-area uniformity and high crystallinity deposited by an antisolvent-assisted spin-coating method acting as the templating layers between the dielectric and thermally evaporated semiconducting layers. The predeposited crystalline monolayers significantly enhance the film crystallinity of upper layers and the overall performance of transistors using these hybrid-deposited semiconducting films, showing a high carrier mobility up to 11.3 cm2 V–1 s–1. Additionally, patterned transistor arrays composed of the templating monolayers are fabricated, yielding an average mobility of 7.7 cm2 V–1 s–1. This work demonstrates a promising method for fabricating low-cost, high-performance, and large-...

The rapid advances in implantable electronic medical devices make supercapacitors highly desirable as power sources. These supercapacitors should be biocompatible, lightweight, miniature and stable without the need for packaging, which unfortunately remains unavailable yet. Here a new family of biocompatible carbon nanotube fibers were synthesized as electrodes to fabricate new supercapacitors that could directly work in physiological fluids including phosphate buffer saline, serum and blood with high energy storage capabilities. For instance, the specific capacitance reached 10.4 F/cm 3 or 20.8 F/g that could be maintained by 98.3% after 10,000 cycles in phosphate buffer saline.

Organo-lead-halide perovskites are promising materials for optoelectronic applications. Perovskite solar cells have reached power conversion efficiencies of over 22%, and perovskite light-emitting diodes have recently achieved over 11% external quantum efficiency. To date, most research on perovskite light-emitting diodes has focused on solution-processed films. There are many advantages of a vapor-based growth process to prepare perovskites, including ease of patterning, ability to batch process, and material compatibility. We investigated an all-vapor perovskite growth process by chemical vapor deposition and demonstrated luminance up to 560 cd/m2.

The rapid rise of power conversion efficiency (PCE) of low cost organometal halide perovskite solar cells suggests that these cells are a promising alternative to conventional photovoltaic technology. However, anomalous hysteresis and unsatisfactory stability hinder the industrialization of perovskite solar cells. Interface engineering is of importance for the fabrication of highly stable and hysteresis free perovskite solar cells. Here we report that a surface modification of the widely used TiO2 compact layer can give insight into interface interaction in perovskite solar cells. A highest PCE of 18.5% is obtained using anatase TiO2, but the device is not stable and degrades rapidly. With an amorphous TiO2 compact layer, the devices show a prolonged lifetime but a lower PCE and more pronounced hysteresis. To achieve a high PCE and long lifetime simultaneously, an insulating polymer interface layer is deposited on top of TiO2. Three polymers, each with a different functional group (hydroxyl, amino, or aromatic group), are investigated to further understand the relation of interface structure and device PCE as well as stability. We show that it is necessary to consider not only the band alignment at the interface, but also interface chemical interactions between the thin interface layer and the perovskite film. The hydroxyl and amino groups interact with CH3NH3PbI3 leading to poor PCEs. In contrast, deposition of a thin layer of polymer consisting of an aromatic group to prevent the direct contact of TiO2 and CH3NH3PbI3 can significantly enhance the device stability, while the same time maintaining a high PCE. The fact that a polymer interface layer on top of TiO2 can enhance device stability, strongly suggests that the interface interaction between TiO2 and CH3NH3PbI3 plays a crucial role. Our work highlights the importance of interface structure and paves the way for further optimization of PCEs and stability of perovskite solar cells.

A novel coaxial triboelectric nanogenerator fiber for both energy harvesting and sensing under deformation was developed by using aligned carbon nanotube sheets as inner and outer electrodes and designing porous structures in triboelectric polymers of polydimethylsiloxane and polymethyl methacrylate. The fiber device was flexible, stretchable, weavable and adaptable for integration with various other electronic devices. Besides the capability of converting multidirectional mechanical energies to electricity with a high durability, it can also sense diverse mechanical stimuli such as pressing, bending, twisting, stretching and vibrating.

Increasing the stability of perovskites is essential for their integration in commercial photovoltaic devices. Halide mixing is suggested as a powerful strategy toward stable perovskite materials. However, the stabilizing effect of the halides critically depends on their distribution in the mixed compound, a topic that is currently under intense debate. Here we successfully determine the exact location of the I and Cl anions in the CH3NH3PbBr3–yIy and CH3NH3PbBr3–zClz mixed halide perovskite lattices and correlate it with the enhanced stability we find for the latter. By combining scanning tunneling microscopy and density functional theory, we predict that, for low ratios, iodine and chlorine incorporation have different effects on the electronic properties and stability of the CH3NH3PbBr3 perovskite material. In addition, we determine the optimal Cl incorporation ratio for stability increase without detrimental band gap modification, providing an important direction for the fabrication of stable perovskite devices. The increased material stability induced by chlorine incorporation is verified by performing photoelectron spectroscopy on a half-cell device architecture. Our findings provide an answer to the current debate on halide incorporation and demonstrate their direct influence on device stability., This work was supported by funding from the Energy Materials and Surface Sciences Unit of the Okinawa Institute of Science and Technology Graduate University, the OIST R&D Cluster Research Program, the OIST Proof of Concept (POC) Program, and JSPS KAKENHI Grant JP18K05266. The work at The University of Toledo was supported by the Center for Hybrid Organic Inorganic Semiconductors for Energy (CHOISE), an Energy Frontier Research Center funded by the Office of Basic Energy Sciences, Office of Science within the US Department of Energy. The theoretical calculation part used the resources of the National Energy Research Scientific Computing Center, which is supported by the Office of Science of the U.S. Department of Energy under Contract DE-AC02-05CH11231. The work at ICN2 is funded by the CERCA Program/Generalitat de Catalunya, and supported by the Severo Ochoa program from Spanish MINECO (Grant No. SEV-2017-0706).

Defects as a result of structural imperfections and/or extrinsic impurities in the perovskite films have a detrimental effect on efficiency and stability of perovskite solar cells (PSCs). Here, we propose to use pre-synthesized crystalline perovskite with perfect stoichiometry to control and lower the density of defects from precursors by the powder engineering method. Compared with raw materials (i.e., PbI2 and FAI) based perovskites, the average efficiency of the PSCs fabricated based on these pre-synthesized perovskite precursors increased from 18.62% to 19.85%. Moreover, the unwanted intermediate chemical compositions (i.e., the unreacted phases and residual solvent) in the raw material-based perovskite films were significantly reduced in the pre-synthesized δ-FAPbI3 and α-FAPbI3 perovskites according to the secondary ion mass spectroscopy depth profiling results. Finally, we obtained the champion efficiency of 22.76% for α-FAPbI3 and 23.05% for FAPb(I0.9Br0.1)3 based PSCs. Long-term operational stability measurements of the encapsulated FAPb(I0.9Br0.1)3 based PSCs showed a slow decay and maintained the efficiency about 88% after 1200 h (T80 > 2000 h). Furthermore, a proof-of-concept integrated perovskite solar module-lithium ion battery-light-emitting diode device was demonstrated.

ABX(3) type metal halide perovskite solar cells (PSCs) have shown efficiencies over 25%, rocketing toward their theoretical limit. To gain the full potential of PSCs relies on the understanding of the device working mechanisms and recombination, the material quality, and the match of energy levels in the device stacks. In this review, the importance of designing PSCs from the viewpoint of surface/interface science studies is presented. For this purpose, recent case studies are discussed to demonstrate how probing of local heterogeneities (e.g., grains, grain boundaries, atomic structure, etc.) in perovskites by surface science techniques can help correlate material properties and PSC device performance. At the solar cell device level with active areas larger than millimeter scale, the ensemble average measurement techniques can characterize the overall average properties of perovskite films as well as their adjacent layers and provide clues to understand better the solar cell parameters. How generation and healing of electronic defects in perovskite films limit the device efficiency, reproducibility, and stability, and induce the time-dependent transient behavior in the current-voltage curves are also the central focus of this review. On the basis of these studies, strategies to further improve efficiency and stability, as well as reducing hysteresis are presented.

A perovskite solar cell fiber is created with a high power conversion efficiency of 7.1% through a controllable deposition method. A combination of aligned TiO2 nanotubes, a uniform perovskite layer, and transparent aligned carbon nanotube sheet contributes to the high photovoltaic performance. It is flexible and stable, and can be woven into smart clothes for wearable applications.

Flexible and wearable solar cells represent a promising direction in the advancement of next-generation energy-harvesting electronics. However, the solar cells in a planar structure cannot meet the requirements of complicated deformations. On the other hand, solar cells based on the one-dimensional structure attract increasing interest as they can stably work under both bending and twisting. Here, a family of fiber-type perovskite solar cells has been designed with impressive photovoltaic performance. They exhibit a high power conversion efficiency of 9.49% that is stable under both bending and twisting. A combination of large crystals of perovskite and aligned carbon nanotube sheets contributes to their excellent properties. Due to their unique fiber shape, they can be further woven into flexible and lightweight power textiles that are promising as the next-generation portable and wearable electronics.

Stretchable supercapacitors are critical for a variety of portable and wearable electronic devices, and they have been typically realized by the use of non-active elastic substrates that do not contribute to the energy storage capability. Here a new family of stretchable supercapacitors is fabricated from cellular carbon nanotube film-based electrodes with high electrochemical performances. They display high specific capacitances that can be maintained by 98.3% after stretching by 140% for 3000 cycles. In addition, their voltage and current windows are tuned by varying the configuration of the film electrode.

A three-dimensionally stretchable supercapacitor is created by designing a novel pyramid structure without the use of an elastic substrate. Compared with previous stretchable supercapacitors that may deform in plane on elastic substrates, these pyramid-structured supercapacitors can be stretched in three dimensions with high stability. Their electrochemical performances are well maintained after stretching in three dimensions for thousands of cycles, and they show both higher energy and power densities compared with the other reported stretchable supercapacitors. In addition, they are breathable due to the designed grooves that produce the pyramid structure, which is particularly promising for many emerging applications such as wearable electronics. This work further provides an effective strategy for developing next-generation flexible electronic devices with high performances.

Metal halide perovskite solar cells (PSCs) have attracted considerable attention from both academia and industry as a promising next-generation technology to harvest solar energy with high power conversion efficiencies (PCEs) at low-cost. At the current stage, efficiencies of these cells have been improved to an impressive level, but the instability issue remains as a major obstacle impeding further commercialization of this technology. In this review, we start with examining the status about the technological aspects of PSC stability research, e.g., stability measurement protocols, their relevance to the realistic operational lifetime, and where we are from the viewpoint of 10-year lifetime. These pressing challenges are correlated with the investigations on the fundamental aspects emphasizing the comprehensive physicochemical understanding of degradation mechanisms in perovskite materials. We examine the various extrinsic and intrinsic factors influencing stability of perovskite materials with different compositions (mixed cations and / or mixed anions, double perovskites, etc.), dimensionality (3D perovskites, 2D perovskites, 2D/3D mixed dimensional perovskites), instability induced by functional layers other than the perovskite layer, and the interactions at various interfaces. On the basis of the analyses of these multiple degradation factors with an emphasis on the holistic microscopic views acquired above, we discuss strategies to improve PSC stability. We finish the review by outlining future research directions that can help achieve long-term stability of PSCs.

Perovskite solar cells (PSCs) have attracted great attention in the past few years due to their rapid increase in efficiency and low-cost fabrication. However, instability against thermal stress and humidity is a big issue hindering their commercialization and practical applications. Here, by combining thermally stable formamidinium-cesium-based perovskite and a moisture-resistant carbon electrode, successful fabrication of stable PSCs is reported, which maintain on average 77% of the initial value after being aged for 192 h under conditions of 85 degrees C and 85% relative humidity (the "double 85" aging condition) without encapsulation. However, the mismatch of energy levels at the interface between the perovskite and the carbon electrode limits charge collection and leads to poor device performance. To address this issue, a thin-layer of poly(ethylene oxide) (PEO) is introduced to achieve improved interfacial energy level alignment, which is verified by ultraviolet photoemission spectroscopy measurements. Indeed as a result, power conversion efficiency increases from 12.2% to 14.9% after suitable energy level modification by intentionally introducing a thin layer of PEO at the perovskite/carbon interface.

Perovskite solar cells have attracted increasing attention due to the possibility of flexible devices compared with silicon-based photovoltaic cells and high energy conversion efficiencies compared with organic photovoltaic cells. Although they have been widely explored in recent years, elastic perovskite solar cells, for the first time, have been realized here by designing a stretchable nanostructured fiber and spring-like modified Ti wire as two electrodes with perovskite materials coated on the modified Ti wire based on a solution process. The elastic perovskite solar cell appears in a fiber format and maintains stable energy conversion efficiencies under stretching.

The conventional connection of energy devices by electrically conducting wires is less efficient and inconvenient, even unavailable in many applications. Herein, a general and effective method is developed to connect energy harvesting or/and storage devices by simply stacking and gently pressing them. The energy devices are touched together and then rapidly fused into one by incorporating an electrically conducting carbon nanotube sheet and a self-healing polymer into a ladder structure. Flexible supercapacitors, perovskite solar cells and their integrated devices are demonstrated. Supercapacitors are fused into various patterns with tunable capacitances, perovskite solar cells are fused into one in series with linearly increasing output voltages, and supercapacitors and perovskite solar cells are also fused into an integrated device to simultaneously realize energy conversion and storage.