Search

Hybrid organic-inorganic perovskite solar cells have attracted considerable attention over the past decade, delivering high power conversion efficiencies over 25%. There still exist challenges regarding precisely regulating perovskite crystallization kinetics due to the random nucleation and disordered diffusion growth in the spontaneous solution chemical reaction process, subsequently leading to poor film quality with chaotic microstructure arrangement and undesired defect states which compromises the photovoltaic performance. Recently, the research priority in the perovskite photovoltaic community has put emphasis on seed templates driving controllable growth of perovskite film, triggering excitement for novel manufacturing technologies. Herein, we provide a systematic overview covering the current pioneering works to comprehend the advances of seed template regulation approaches and the underlying mechanism in terms of microstructure evolution and optoelectronic properties. The intense search regarding constructing representative perovskite single and polycrystalline crystals is provided to elaborate on the prominent roles of seed templates. [Display omitted] • In-depth theoretical mechanisms regarding heteroepitaxial growth and advanced regulation strategies are provided. • Conceptual insights into structural properties in perovskite polycrystals are proposed. • The promising progress regarding controlling over the perovskite single crystals growth is introduced. [ABSTRACT FROM AUTHOR]

The undesired segregation of inactive secondary phase that randomly distributed across the perovskite film is detrimental to charge-carrier transport dynamics and light stability. However, in-depth studies for understanding the underlying chemical reaction mechanism and the relationship between phase structural configuration and physical properties are still lacking. Herein, the segregation behavior of the inactive secondary phase and the underlying microcosmic mechanism regarding ionic chemical replacement reaction and lattice reconfiguration process are systematically elaborated. A high-quality perovskite-PbI 2 heterojunction film is constructed via converting the three-dimensional PbI 2 photoactive phase into a two-dimensional inactive phase, alleviating the energetic disorder of carrier dynamics and photochemical dissociation. The resultant perovskite solar cells achieve an efficiency of 24.23% with excellent light-resistance. The dissociation energetics of phase dimensional structure is theoretically analyzed. This work provides new insights into crystal structure design for constructing high-quality perovskite heterojunction devices. [Display omitted] • The segregation behavior of secondary phase in perovskite is rationally regulated based on dimensional engineering strategy. • Evolution mechanism of ion-competition reaction and lattice reconstruction process is revealed in depth. • The energetic disorder of carrier dynamics is well ameliorated based on the formed build-in type-Ⅰ band alignment. • Perovskite-2D PbI 2 heterojunction devices achieve high efficiency of 24.23% with excellent long-term light-resistance. [ABSTRACT FROM AUTHOR]

Abstract The thermal conductivity of a phase change material (PCM) is an important parameter that affects the heat transfer characteristics of PCM. In this study, the fractal theory is conducted to study the prediction model of the effective thermal conductivity of fatty acid/carbon material composite PCMs in the solid phase. Based on the Sierpinski carpet model of fractal geometry, a series of fractal units with different fractal dimensions are developed for the fatty acid/carbon material composite PCMs. Combined with a self-similar principle and thermal resistance network theory, a general solution for the dimensionless effective thermal conductivity of a typical Sierpinski carpet fractal unit is then derived. Further, dimensionless effective thermal conductivity prediction models of three typical structures of fatty acid/carbon material composite PCMs are obtained by comparing the experimental data. Finally, the thermal conductivity prediction model from this study demonstrated a better reliability than that of the commonly used QP prediction model and Maxwell-Eucken prediction model. This prediction model could be used to predict the effective thermal conductivity of composite PCMs. Highlights • Equivalent model of typical Sierpinski carpet is firstly proposed. • General solutions of typical Sierpinski carpet structures are derived. • Model can predict the effective thermal conductivity of composite PCMs. • Proposed prediction model shows a good reliability and high accuration. [ABSTRACT FROM AUTHOR]

Abstract Even though TiO 2 is the most widely used electron transport layer (ETL) in high-efficiency perovskite solar cells (PSCs), ultraviolet photocatalysis and existence of intrinsic oxygen vacancies result in interfacial charge recombination and poor long-term photo-stability for TiO 2 -based PSCs under full spectral continuous illumination. To solve the issues, here we report dopamine-capped TiO 2 nanoparticles as ETL via chelating effect to improve interfacial binding with perovskite active layer. The introduction of dopamine can substantially reduce oxygen vacancies and suppress deep trap states within TiO 2. In addition, the terminal amino groups in dopamine can passivate the uncoordinated Pb atoms and decrease the Pb-I/Br antisite defects on the interface of perovskite/TiO 2. As an interfacial crosslinking agent, dopamine can not only reduce charge-accumulation and charge-recombination rate, but also increase charge-extraction efficiency at the TiO 2 and perovskite interface. Based on the dopamine-capped TiO 2 nanoparticles surface, the corresponding planner Cs 0.05 FA 0.81 MA 0.14 PbI 2.55 Br 0.45 PSCs deliver a power conversion efficiency of nearly 21% with negligible hysteresis. Moreover, unencapsulated devices retain 80% of their initial performance after 1200 h operation under constant full-sun illumination in nitrogen atmosphere. Ideally, this chemical-bath-deposited dopamine-modified TiO 2 provides an effective commercialized route for efficient and photostable planar PSCs. Graphical abstract fx1 Highlights • Dopamine-capped TiO 2 is obtained via sub-150 °C solution-processed method. • Defects of TiO 2 are decreased via chelating effect of dopamine. • Dopamine can effectively crosslink perovskite/TiO 2 interface. • Dopamine leads to a PCE of 20.93% with negligible hysteresis. • PSC retains ~80% of its performance under continuous 1200 h full spectral illumination. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Systematical summary and discussion of colloidal PC sensors from materials, structures, and analysis methods. • MOF-based PCs, shape-memory polymer PCs, PCs composed of nature materials etc. are firstly summarized. • Hollow mesoporous PC, metastable PCs etc. are reviewed to emphasize the significance of structures in developing colloidal PC sensors. • PC sensor array for cross-reactive analysis system and time/spatial resolved reflection spectra are highlighted and discussed in details. • Firstly present 'time/spatial resolved reflection spectra' analysis method. Abstract Colloidal photonic crystal (PC) sensors have been well developed due to their unique advantages in preparation and functionalization, and have been applied into diverse sensing systems. Recently, many breakthroughs about new-type colloidal PC sensors with fast respond speed, high sensitivity and excellent selectivity have been achieved. In this review, we summarize the recent advances of colloidal PC sensors from aspects of materials, structures, and analysis methods, to exhibit the diverse developing strategies. Firstly, an overview of colloidal PC sensors composed of new responsive materials is presented. Next, the unique structures are systematically summarized according to their scale increasing from nanoscale to macroscale, including the colloidal nanoparticles with novel structures and morphologies, the micro-sized PC units, and the integrated PC devices. Then, two series of new analysis methods, cross-reactive analysis based on PC sensors and time/spatial resolved reflection spectra analysis, are highlighted and discussed in details because they can greatly improve the selectivity of recognitions. Finally, a summary and some perspectives on several development directions in this attractive research field are presented. [ABSTRACT FROM AUTHOR]

Inspired by light/sound trapping in whispering-gallery, a light trapping structure mimicking whispering-gallery (WG) structure is constructed on perovskite active layer for antireflection and light harvesting via simply imprinted process with robust microstructure stamp for perovskite solar cells (PSCs). The WG structured perovskite films can achieve light trapping by optical feedback and gradually absorption. The crystallization and size of perovskite are improved by the imprinting process with robust micro-patterned stamp. Moreover, this method can efficiently accelerate electron-hole separation and suppress recombination by extract tentacles of the arrayed column structure. Consequently, the power conversion efficiency of the whispering-gallery structured PSC is improved to 19.80%, which is ca. 29.4% higher than that of the non-imprinted PSC (15.30%). [ABSTRACT FROM AUTHOR]

The performance of large-area perovskite solar cells (PSCs) is confined to the non-uniformity edge-coating and crystalline defects. Focusing on the critical requirement of large-area uniform and compact crystallized perovskite film for efficient PSCs, here, an inkjet manipulated approach is introduced for controlling the thin-film perovskite growth in a mesoporous solar cell device structure. The ink droplet wetting behavior on mesoporous substrate, the physical properties of solutions have been systematically investigated. Uniform liquid membrane was obtained via precisely controlled micro-droplets by inkjet-printing. Mesoporous substrates guarantee fast and complete coalescence of the precursor droplets, and limit random diffusion of the precursor solution. Homogeneous PbI 2 film leads to a compact perovskite film with micro-scale crystalline grains, which enables PSCs high power conversion efficiencies (PCEs) of 18.64% for small area (0.04 cm 2 ) and 17.74% for large area (2.02 cm 2 ). The enhanced performance can be ascribed to improved uniformity of the perovskite film morphology, favorable perovskite crystallite orientation, large grain size (> 2 µm) and less grain boundaries. Inkjet manipulation provides a facile approach to fabricate large-area and high-quality films for future optoelectronics, including field effect transistors, light-emitting diodes, and sensor devices. [ABSTRACT FROM AUTHOR]

Objective To systematically evaluate the diagnostic performance of increased signal intensity within the resection cavity on fluid-attenuated inversion recovery (FLAIR) sequences for detection of progression in patients with glioma through performing a meta-analysis. Methods PubMed, Web of Science, Embase, Cochrane Library, and China National Knowledge Infrastructure were searched for potentially relevant literature. The study characteristics and relevant data were extracted. We estimated the pooled sensitivity, specificity, positive likelihood ratios, negative likelihood ratios, and diagnostic odds ratio and constructed summary receiver operating characteristics curves to identify the diagnostic value of FLAIR signal increase for detection of glioma progression. Results A total of 4 studies with 438 patients were included. The pooled sensitivity and specificity of increased signal intensity in FLAIR sequences in the resection cavity for detection of glioma progression were 0.36 (95% confidence interval 0.31–0.42) and 0.93 (95% confidence interval 0.86–0.97), respectively. The area under the curve was 0.7505. Subgroup analyses also were performed according to different patient sources, tumor grades, and definitions of progression. No significant publication bias was found in the meta-analysis ( P = 0.85). Conclusions Our results suggested that increased signal intensity within the resection cavity on FLAIR sequences could indicate tumor progression early with high specificity in patients with glioma. This readily accessible sign could implicate closer monitoring and could be crucial for therapeutic decisions and outcome. However, because of the limited number of studies, more well-designed studies are warranted to further verify our results and elucidate the underlining mechanisms. [ABSTRACT FROM AUTHOR]

The collection and utilization of water power as clean energy have made tremendous progress in recent years, where the droplet-based triboelectric power generation is one of the most studied fields. Current researches mainly focus on the droplet-based single-electrode triboelectric generation mode; however, the low power output greatly limits the practical applications. By contrast, the droplet-based bi-electrode freestanding TENG (DBE-TENG) show great potential for enhancing the output, while the charge transfer mechanism of droplets evolution on the DBE-TENG is still ambiguous. Here we demonstrate that for a DBE-TENG, the maximum current output of the droplet at different droplet impact positions exhibits a sinusoidal-like variation, and the current output can be improved by two orders of magnitude by simply controlling the droplet impacting positions. Furthermore, an asymmetrical-capacitance-induced charge transfer mechanism is proposed, which well elucidates the prominent current output enhancement and the sinusoidal-like variation. In addition, the current output enhancing strategy is applicable under different kinds of dielectric materials and conditions (inclined conditions and different Weber numbers), with the maximum enlargement up to 263 times. The findings deepen the understanding of the charge transfer mechanism for bi-electrode triboelectric nanogenerators, and will be of significance for improving the efficiency of sustainable energy harvesting. [Display omitted] • The current output can be improved by two orders of magnitude by regulating the droplet positions. • Asymmetrical-capacitance-induced charge transfer mechanism dominates the power output. • The maximum current output at different droplet impact positions exhibits a sinusoidal-like variation. • The current enhancing strategy is universal under different dielectric materials and conditions. [ABSTRACT FROM AUTHOR]

Non-contact sensors, intelligent electronics that interact with surrounding information with no physical contact, are highly desirable for human-machine interaction. Due to the increased sensing distance and expanded operation scope, it is anticipated the non-contact device exhibiting enhanced electrical output and detection range. Here, freeze-drying assisted 3D printing approach is employed to fabricate cellulose nanofiber (CNF)/MXene-based deep-trap hierarchical architecture for non-contact triboelectric nanogenerators, which exhibit excellent sensing performance for multi-direction motion monitoring. The intermolecular hydrogen bonding between CNF and MXene nanosheets facilitates the formation of a well-dispersed ink with suitable viscoelasticity for 3D printing. The incorporation of MXene nanosheets provides the printed scaffold with more open pores for increased charge generation. Meanwhile, the high electron trapping capability of MXene leads to a weakened electron escaping tendency and an increased decay time, which are beneficial for the device's non-contact voltage output. Based on the as-prepared non-contact sensor, an all-printed sensing array and a 3D sensor are demonstrated for multi-site and multi-dimension motion trajectories monitoring, indicating its great potential in healthcare, safe navigation, and artificial intelligence. A freeze-drying-assisted 3D printing strategy is employed to fabricate cellulose nanofiber/MXene-based hierarchical aerogel scaffold for non-contact sensors with high charge trapping capability and electrical output. The strategy is demonstrated to fabricate a sensing array and a 3D sensor for muti-site and multi-dimension position detection and moving trajectory monitoring. [Display omitted] • Through a freeze-drying assisted 3D printing approach, CNF/MXene-based hierarchical architecture is fabricated for non-contact triboelectric sensor. • The high electron trapping capability of MXene leads to a weakened electron escaping tendency and an increased decay time for improved device performance. • Based on the 3D-printed TENG, a non-contact sensing system is designed for multi-direction motion monitoring. [ABSTRACT FROM AUTHOR]

The brittleness of perovskite (PVK) film restrains the development and application of the flexible perovskite solar cells (FPSCs). We utilize the polyurethane elastomers with disulfide bonds (PUDS) as a self-healing polymer to construct self-healing FPSCs and strengthen the self-healed perovskite film by the phase-locked state. The PUDS efficiently enhances the flexibility and self-healing properties of FPSCs. The champion efficiencies of MAPbI 3 on rigid and flexible substrates with PUDS are 20.30% and 17.19%, respectively. Importantly, the efficiency of cracked FPSC after thermal self-healing (80 °C) has been recovered from 12% (Broken: 2.06%) of the initial efficiency (17.19%) to 88% (Recovery: 15.12%). Besides, the efficiency of FPSC with PUDS maintains 95% of the initial value after 3000 h stored in glove box. This strategy provides an effective approach for developing flexible electronics. [Display omitted] • Polyurethane with disulfide bonds achieve the self-healing flexible perovskite solar cells by the phase-locked dynamic bonds. • The dynamic bonds of PUDS transform to the phase-locked state strengthening the self-healed perovskite film. • The efficiency of the cracked FPSC recovers from 12% (Broken: 2.06%) to 88% (Recovery: 15.12%) of the initial efficiency (17.19%) after the multiple bending-heal. • The FPSC with PUDS maintains 84% of the initial PCE after 4000 bending cycles at the radius of 3 mm. [ABSTRACT FROM AUTHOR]

The unique properties of metal halide perovskites give them great potential for applications in portable and wearable optoelectronics. However, the intrinsic brittleness of perovskites favors easy crack propagation that deteriorates the optoelectronic performance of the devices. Inspired by nacre, we propose flexible perovskite thin films fabricated by antisolvent-assisted self-encapsulation of polymer and imprinting techniques during crystallization. Such an approach results in synchronous formation of polymer-glued perovskite grains exhibiting nacre-like "brick-and-mortar" structure. The deformable composite architecture bonding hemisphere-shaped grating (HG) and porous photonic crystal (PC) (HG-PC) improves its crystalline quality and light-harvesting capability. An HG-PC photodetector (PD) with high responsivity of 17.31 A/W and detectivity of 5.02 × 1013 Jones is achieved. Our flexible HG-PC PD retains 95% of the initial photocurrent after 1000 bending cycles at 2 mm curvature radius. This solvent-driven self-encapsulation strategy offers an innovative and universal approach for highly efficient flexible optoelectronics. [Display omitted] • The synergistic effect of "brick-and-mortar" structure and deformable photonic architecture endows flexible perovskite photodetector with high mechanical robustness and durability • A perovskite photodetector with high responsivity of 17.31 A/W and detectivity of 5.02 × 1013 Jones is achieved. [ABSTRACT FROM AUTHOR]

• The evolution of 2D perovskites based on multi-characteristic organic spacers is approached. • Impacts of the organic spacers on photophysical properties and film quality of 2D perovskites are discussed. • Several strategies to select and optimize the organic spacers for enhancing photovoltaic characteristics are proposed. [Display omitted] Two-dimensional (2D) perovskites have been attracting extensive attention due to their intrinsic stability compared with their three-dimensional (3D) counterparts. These materials are widely tailorable in composition, structure, and bandgap, and provide an intriguing playground for the solid-state chemistry and physics communities to uncover structure-property relationships. In the field of photovoltaic, the fabricated 2D perovskite solar cells (PSCs) have achieved high stability as well as sustainable breakthrough in power conversion efficiency (PCE). However, the PCE of 2D PSCs still lags far behind their 3D counterpart, which is attributed to the special physicochemical properties of organic ligands. This review focuses the 2D halide perovskites from a structural perspective, namely the Ruddlesden-Popper (RP) phases, Dion-Jacobson (DJ) phases, alternating cation in the interlayer space (ACI) phases and mixed organic ligands phases, which stems from the diversity and versatility of spacers. Then the impacts of the species, chemical compositions, and physical characteristics of spacers on 2D perovskites, especially on the structure, carrier behavior, and the specific properties of solar cells, were discussed. Finally, several strategies on the rational selection of novel spacers are elucidated, and an outlook toward high-performance of 2D PSCs is presented. [ABSTRACT FROM AUTHOR]

Flexible perovskite solar cells are promising power source candidates in wearable and portable electronics. However, the performance of flexible perovskite solar cells still lags the values reported in rigid devices. This issue is mainly due to the lack of suitable electrodes which possess low sheet resistance, high optical transmittance, and smooth surface. Here, we proposed a flexible electrode based on solution-processed silver grids. With the patterned micro-bubbles as templates, high-resolution sliver grids electrodes were fabricated, which showed a sheet resistance of 7.9 Ω/sq and optical transmittance over 85% (including the substrate, from 375 nm to 900 nm). Besides, the embossed sliver grids can assist the growth of perovskite crystals and provide localized channels for charge carrier transport. The corresponding flexible perovskite solar cells based on these flexible sliver grids electrodes achieved a power conversion efficiency of 18.49% with remarkable flexibility, which enhanced about 20% compared to the control devices. An embossed transparent electrode based on high-definition flexible Ag grids (FAGs) was fabricated by a self-assembled method with patterned bubbles as templates. The flexible transparent electrode based on highly ordered Ag grids presented high optical transmittance (>85% including substrate, from 375 to 900 nm) and low sheet resistance (~7.9 Ω/sq). The microstructures on the surface of the FAGs can optimize the film morphology of perovskite thin films by slowing down the nucleation process of perovskite precursor. In addition, the highly ordered embossed Ag grids served as localized channels for charge carrier transport, leading an efficient charge extraction on the interface between charge transfer layer and perovskite layer. The corresponding flexible perovskite solar cells based on the FAGs electrodes achieved a power conversion efficiency of 18.49% with remarkable flexibility, which was about 20% higher than the control devices. [Display omitted] • An embossed transparent electrode based on high-definition flexible Ag grids (FAGs) was fabricated by a printable self-assembled approach with patterned bubbles as templates. • The embossed Ag grids also served as localized channels for charge carrier transport and resulted in an efficient charge extraction. • The corresponding flexible perovskite solar cells achieved a power conversion efficiency of 18.49%. [ABSTRACT FROM AUTHOR]

Graphene has important application prospects in many fields, and is considered a revolutionary material in the future. The biocompatibility of graphene and its safety issues have drawn much attention. Possible toxicities of a nanomaterial might be concerned with cell deaths, releasing of damage-associated molecular patters (DAMPs), inflammation, risks of tumorigenesis etc. In the current study, we investigated the long-term pulmonary exposure model of graphene and carbon black and discovered that long-term pulmonary exposure of the materials led to lung cancer metastasis and progression. Notably, pulmonary exposure of graphene or carbon black induced cell necrosis and the release of the DAMP, namely, mitochondrial DNA (mtDNA), which is a potent stimulator for elevating the secretion of Wnt ligands in alveolar macrophages (AMs). The Wnt-activating macrophages contributed to the formation of premetastatic niches in lung tissues by enhancing the stemness potential of cancer cells and promoting their generation and proliferation. The growth of metastatic cancer induced by exposure of carbon-based nanomaterials could be effectively inhibited by treating mice with a Wnt inhibitor. Taken together, our findings elucidate the how the pulmonary cell deaths induced by graphene reshaped the tumor microenvironment by releasing DAMPs and promoting tumor metastasis, which throws the light on the relationship between nanomaterial toxicity and its tumorigenesis risk. [Display omitted] • Long-term exposure of graphene in mice via the nose-only exposure system promoted tumor pulmonary metastasis. • Graphene-induced necrotic cells released mtDNA, and enhanced the secretion of Wnt ligands in alveolar macrophages via TLR9. • Graphene-induced elevation of Wnt ligands activated Wnt signaling in and enhanced stemness and metastasis of cancer cells. • A Wnt inhibitor LGK974 effectively attenuated the graphene-induced tumor growth and pulmonary metastasis. [ABSTRACT FROM AUTHOR]