The non-uniform distribution of colloidal particles in perovskite precursor results in an imbalanced response to the shear force during flexible printing process. Herein, it is observed that the continuous disordered migration occurring in perovskite inks significantly contributes to the enlargement of colloidal particles size and diminishes the crystallization activity of the inks. Therefore, a molecular encapsulation architecture by glycerol monostearate to mitigate colloidal particles collisions in the precursor ink, while simultaneously homogenizing the size distribution of perovskite colloids to minimize their diffusion disparities, is devised. The utilization of colloidal particles with a molecular encapsulation structure enables the achievement of uniform deposition during the printing process, thereby effectively balancing the crystallization rate and phase transition in the film and facilitating homogeneous crystallization of perovskite films. The large-area flexible perovskite device (1.01 cm2 and 100 cm2) fabricated through printing processes, achieves an efficiency of 24.45% and 15.87%, respectively, and manifests superior environmental stability, maintaining an initial efficiency of 91% after being stored in atmospheric ambiences for 150 days (unencapsulated). This work demonstrates that the dynamic evolution process of colloidal particles in both the precursor ink and printing process represents a crucial stride toward achieving uniform crystallization of perovskite films.
Organic-inorganic hybrid perovskites are considered ideal candidates for future photovoltaic applications due to their excellent photovoltaic properties. Although solution-printed manufacturing has shown inherent potential for the low-cost, high-throughput production of thin-film semiconductor electronics, the high-quality and high-reproducibility deposition of large-area perovskite remains a bottleneck that restricts their commercialization due to the droplet coffee-ring effect (CRE). In this study, these issues are addressed by introducing an in situ polymer framework. The 3D framework formed by spontaneous cross-linking improves the precursor viscosity and homogenizes its heat diffusion coefficient, counteracting the lateral capillary flow of the colloidal particles and anchoring their flocculent movement. Thus, the Marangoni convection intensity is properly controlled to ensure high-quality perovskite films, which significantly enhances reproducibility in printing efficient photovoltaics by mitigating the CRE. Subsequently, the perovskite solar cells and modules achieve power conversion efficiencies of 23.94 and 17.53%, and exhibit positive environmental stability, retaining over 90 and 78% efficiency after storage for 2500 and 1600 h, respectively. This work may serves as a foundation for exploring precursor rheology to match the homogeneous deposition requirements of perovskite photovoltaics and facilitating the advancement of their printing manufacturing and commercialization transition.
Flexible perovskite solar cells (f-PSCs) as a promising power source have grabbed surging attention from academia and industry specialists by integrating with different wearable and portable electronics. With the development of low-temperature solution preparation technology and the application of different engineering strategies, the power conversion efficiency of f-PSCs has approached 24%. Due to the inherent properties and application scenarios of f-PSCs, the study of strain in these devices is recognized as one of the key factors in obtaining ideal devices and promoting commercialization. The strains mainly from the change of bond and lattice volume can promote phase transformation, induce decomposition of perovskite film, decrease mechanical stability, etc. However, the effect of strain on the performance of f-PSCs has not been systematically summarized yet. Herein, the sources of strain, evaluation methods, impacts on f-PSCs, and the engineering strategies to modulate strain are summarized. Furthermore, the problems and future challenges in this regard are raised, and solutions and outlooks are offered. This review is dedicated to summarizing and enhancing the research into the strain of f-PSCs to provide some new insights that can further improve the optoelectronic performance and stability of flexible devices.
Optical imaging holds great promise for monitoring bacterial infectious processes and drug resistance with high temporal-spatial resolution. Currently, the diagnosis of deep-seated bacterial infections in vivo with fluorescence imaging, including near-infrared (NIR) fluorescence imaging technology, remains a significant challenge due to its limited tissue penetration depth. In this study, we developed a highly specific targeting probe, Cy7-Neo-NO2, by conjugating a bacterial 16S rRNA-targeted moiety, neomycin, with a bacterial nitroreductase (NTR)-activated NIR photoacoustic (PA) scaffold using our previously developed caged photoinduced electron transfer (a-PeT) approach. This conjugation effectively resolved probe aggregation issues in physiological conditions and substantially enhanced its reactivity toward bacterial NTR. Notably, Cy7-Neo-NO2 enabled the first in situ photoacoustic imaging of pneumonia induced by methicillin-resistant Staphylococcus aureus (MRSA), as well as the detection of bacteria within tumors. Furthermore, upon NIR irradiation, Cy7-Neo-NO2 successfully inhibited MRSA growth through a synergistic effect combining photothermal therapy and photodynamic therapy. Our results provided an effective tool for obtaining exceptional PA agents for accurate diagnosis, therapeutic evaluation of deep-seated bacterial infections in vivo, and intratumoral bacteria-specific recognition.
The research of delayed fluorescence (DF) has been a hot topic in biological imaging. However, the development of analyte-triggered small molecule DF probes remains a considerable challenge. Herein a novel excited-state intramolecular proton transfer-delayed fluorescence (ESIPT-DF) approach to construct analyte-stimulated DF probes was reported. These new classes of ESIPT-DF luminophores were strategically designed and synthesized by incorporating 2-(2'-hydroxyphenyl)benzothiazole (HBT), a known ESIPT-based fluorophore, as acceptor with a series of classic donor moieties, which formed a correspondingly twisted donor-acceptor pair within each molecule. Thereinto, HBT-PXZ and HBT-PTZ exhibited significant ESIPT and DF characters with lifetimes of 5.37 and 3.65 µs in the solid state, respectively. Furthermore, a caged probe HBT-PXZ-Ga was developed by introducing a hydrophilic d-galactose group as the recognition unit specific for ß-galactosidase (ß-gal) and ESIPT-DF blocking agent and applied to investigate the influence of metal ions on ß-gal activity on the surface of Streptococcus pneumoniae as a convenient tool. This ESIPT-DF "turn-on" approach is easily adaptable for the measurement of many different analytes using only a predictable modification on the caged group without modification of the core structure.
Fluorescent Dyes , Protons , Spectrometry, Fluorescence , Fluorescent Dyes/chemistry , Optical Imaging
Deep traps stemming from the defects formed at the surfaces and grain boundaries of the perovskite films are the main reasons of nonradiative recombination and material degradation, which significantly affect efficiency and stability of perovskite solar cells (PSCs). Here, a spontaneous internal encapsulation strategy was developed by constructing a dual interfacial perovskite heterojunction at the top and buried interface of the three-dimensional (3D) perovskite film. The spacer cations of the two-dimensional (2D) perovskite structure interacted strongly with the 3D perovskite to passivate the defects and optimize the energy level alignment. Meanwhile, the interfacial perovskite heterojunction underearth delayed the crystallization speed and improved the crystallization quality of the upper 3D perovskite. Thanks to these positive effects, the PSC exhibited a power conversion efficiency of 22.92% with good reproducibility. Significantly, the unencapsulated device with the dual interfacial perovskite heterojunction maintained 88% of its initial efficiency after 2900 h under 65 ± 5% RH in air.
The multiple quantum wells (QWs) distribution in low-dimensional perovskite films hinders charge transport due to the fundamental difficulty of controlling crystal growth from precursor solutions, yielding poorly homogeneous low-dimensional perovskite solar cells (PSCs), especially in upscaling fabrication. Here, efficient low-dimensional PSCs are realized by modulating the colloidal assembly behavior in the precursor solution to induce intermediate structures. In combination with in situ liquid time-of-flight secondary ion mass spectrometry, the assembly behavior of organic cations involved lead iodide-dominated colloidal soft framework is visualized by investigating the precursor species differences under hydrogen bonding interactions. Subsequently, solid-state reactions emerge and the formamidine (FA)-based perovskite films exhibit significantly suppressed multiple QWs distribution. Encouragingly, the FA device (n=9, by meniscus-assisted coating) achieves a power conversion efficiency (PCE) of 20.28 % for a size of 0.04â cm2 and a PCE of 15.35 % for a mini-module of 16.94â cm2 with superior stability.
The inhomogeneity, poor interfacial contact, and pinholes caused by the coffee-ring effect severely affect the printing reliability of flexible perovskite solar cells (PSCs). Herein, inspired by the bio-glue of barnacles, a bionic interface layer (Bio-IL) of NiOx /levodopa is introduced to suppress the coffee-ring effect during printing perovskite modules. The coordination effect of the sticky functional groups in Bio-IL can pin the three-phase contact line and restrain the transport of perovskite colloidal particles during the printing and evaporation process. Moreover, the sedimentation rate of perovskite precursor is accelerated due to the electrostatic attraction and rapid volatilization from an extraordinary wettability. The superhydrophilic Bio-IL affords an even spread over a large-area substrate, which boosts a complete and uniform liquid film for heterogeneous nucleation as well as crystallization. Perovskite films on different large-area substrates with negligible coffee-ring effect are printed. Consequently, inverted flexible PSCs and perovskite solar modules achieve a high efficiency of 21.08% and 16.87%, respectively. This strategy ensures a highly reliable reproducibility of printing PSCs with a near 90% yield rate.
Bionics , Calcium Compounds , Calcium Compounds/chemistry , Oxides/chemistry , Reproducibility of Results , Titanium
pH homeostasis is essential for alkaliphiles, given their widespread use in biotechnological applications. However, quantitative monitoring of alkaline pH in alkaliphiles remains challenging. Here, we synthesized for the first time, a thermally activated delayed fluorescent (TADF) pH probe: NI-D-OH. Our probe exhibits a good linear relationship between fluorescence intensity and pH in the neutral to alkaline range (pH 7.0-8.6), as well as long-lived TADF emission. We further show that NI-D-OH can be used to monitor intracellular pH in living organisms, and evaluate the effect of Na+ on the pH homeostasis, demonstrating the potential for alkaline pH monitoring and time-resolved fluorescence imaging.
Biotechnology , Fluorescent Dyes , Fluorescence , Fluorescent Dyes/chemistry , Hydrogen-Ion Concentration
The existing conformation of the active layer is defective for employment of semitransparent organic solar cells (ST-OSCs) in solar windows. Herein, scalable solar windows are successfully printed by introducing a pseudo-planar heterojunction (PPHJ) structure. The PPHJ structure can effectively improve the average visible transmittance (AVT) value while boosting the power conversion efficiency (PCE) of semitransparent devices due to the reduced optical loss. The universality of the PPHJ structure in the preparation of ST-OSCs is proved. Furthermore, an inset of a superhydrophobic patterned soft insertion layer (PSIL) in the encapsulated window improves the waterproof performance without losing transparency. Accordingly, the semitransparent devices based on the 2,2'-((2Z,2'Z)-((12,13-bis(2-ethylhexyl)-3,9-diundecyl-12,13-dihydro-[1,2,5]thiadiazolo[3,4-e]thieno[2â³,3â³:4',5']thieno[2',3':4,5]pyrrolo[3,2-g]thieno[2',3':4,5]thieno[3,2-b]indole-2,10-diyl)bis(methanylylidene))bis(5,6-difluoro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))dimalononitrile (Y6) system afford a maximal efficiency of 14.62%, with a considerable AVT of 20.42%, and the resultant solar windows achieve a stabilized efficiency of 13.34% with excellent waterproof performance. Moreover, the PCE of the unilateral broken solar windows retains 70.6% of the initial efficiency after being placed under simulated rainfall conditions for 1200 h at room temperature.
Highly efficient and stable quasi-2D hybrid perovskite solar cells (PSCs) using hydrophobic 4-(trifluoromethyl) benzylamine (4TFBZA) as the spacer cation are successfully demonstrated. It is found that the incorporation of hydrophobic 4TFBZA into MAPbI3 can effectively induce a spontaneous upper gradient 2D (SUG-2D) structure, passivate the trap states, and restrain the ion motion. Meanwhile, the strong hydrogen bonding of F···HN between 4TFBZA ions and methylamine ions can effectively suppress the decomposition of perovskite, which gives the device a better thermal stability. Besides, due to the SUG-2D structure with hydrophobic 4TFBZA, the device also exhibits a better moisture stability. The SUG-2D-structure-based device exhibits a power conversion efficiency of 17.07% with a high open-circuit voltage of 1.10 V and a notable fill factor of 71%. This work provides a new strategy for constructing efficient and stable quasi-2D PSCs, and it is an inspiration for the packaging strategy of perovskites.
A washable perovskite solar cell with high efficiency (over 11%) and outstanding crumpling durability (maintaining 81.2% after 100 cycles crumpling) is demonstrated herein by combining the flexible self-encapsulation method with a waterproof glue coated substrate.
Dramatic development in perovskite solar cells (PSCs) and the widespread application of wearable electronics have attracted extensive research in the area of large-scale flexible solar power sources based on PSCs. Manufacturing of flexible PSCs by printing is considered to be one of the most potential methods. However, it is still a great challenge to print large-area uniform hole transport layers (HTLs) on a rough and soft plastic substrate to achieve flexible PSCs with high efficiency and good stability. Herein, we synthesized a viscous poly(3,4-ethylene dioxythiophene):graphene oxide (PEDOT:GO) gel and then blade-coated the gel by high-speed shearing to achieve high-quality HTLs with scalable size. The glued HTLs exhibit high viscosity, electrical conductivity, and mechanical flexibility, which enhance the adhesive ability and protect the brittle ITO electrode and perovskite crystals. Due to the gelatinous HTLs, we achieved an optimal efficiency of the flexible PSCs (1.01 cm2) of 19.7%, while that of the large-area flexible perovskite module (25 cm2) exceeded 10%. This is the highest efficiency for reported flexible MAPbI3 PSCs (1.01 cm2). Furthermore, the efficiency retention of the PSCs remains over 85% after 5000 bending cycles, which is of great significance for the practical application of PSCs in portable and wearable electronics.
Tin-based perovskite solar cells (PSCs) demonstrate a potential application in wearable electronics due to its hypotoxicity. However, poor crystal quality is still the bottleneck for achieving high-performance flexible devices. In this work, graphite phase-C3 N4 (g-C3 N4 ) is applied into tin-based perovskite as a crystalline template, which delays crystallization via a size-effect and passivates defects simultaneously. The double hydrogen bond between g-C3 N4 and formamidine cation can optimize lattice matching and passivation. Moreover, the two-dimensional network structure of g-C3 N4 can fit on the crystals, resulting an enhanced hydrophobicity and oxidation resistance. Therefore, the flexible tin-based PSCs with g-C3 N4 realize a stabilized power conversion efficiency (PCE) of 8.56 % with negligible hysteresis. In addition, the PSCs can maintain 91 % of the initial PCE after 1000â h under N2 environment and keep 92 % of their original PCE after 600â cycles at a curvature radius of 3â mm.
The power conversion effciency (PCE) of flexible perovskite solar cells (PSCs) has increased rapidly, while the mechanical flexibility and environmental stability are still far from satisfactory. Previous studies show the environmental degradation and ductile cracks of perovskite films usually begin at the grain boundaries (GBs). Herein, sulfonated graphene oxide (s-GO) is employed to construct a cementitious GBs by interacting with the [PbI6]4- at GBs. The resultant s-GO-[PbI6]4- complex can effectively passivate the defects of vacant iodine, and the devices with s-GO exhibit remarkable waterproofness and flexibility due to the tough and water-insoluble GBs. The champion PCE of 20.56% (1.01 cm2) in a device treated with s-GO is achieved. This device retains 90% of its original PCE after 180 d stored in the ambient condition, as well as over 80% retention after 10,000 bending cycles at a curvature radius of 3 mm.
The translation of unparalleled efficiency from the lab-scale devices to practical-scale flexible modules affords a huge performance loss for flexible perovskite solar cells (PSCs). The degradation is attributed to the brittleness and discrepancy of perovskite crystal growth upon different substrates. Inspired by robust crystallization and flexible structure of vertebrae, herein, we employ a conductive and glued polymer between indium tin oxide and perovskite layers, which simultaneously facilitates oriented crystallization of perovskite and sticks the devices. With the results of experimental characterizations and theoretical simulations, this bionic interface layer accurately controls the crystallization and acts as an adhesive. The flexible PSCs achieve the power conversion efficiencies of 19.87% and 17.55% at effective areas of 1.01 cm2 and 31.20 cm2 respectively, retaining over 85% of original efficiency after 7000 narrow bending cycles with negligible angular dependence. Finally, the modules are assembled into a wearable solar-power source, enabling the upscaling of flexible electronics.
Perovskite solar cells (PSCs) are a promising photovoltaic technology for stretchable applications because of their flexible, light-weight, and low-cost characteristics. However, the fragility of crystals and poor crystallinity of perovskite on stretchable substrates results in performance loss. In fact, grain boundary defects are the "Achilles' heel" of optoelectronic and mechanical stability. We incorporate a self-healing polyurethane (s-PU) with dynamic oxime-carbamate bonds as a scaffold into the perovskite films, which simultaneously enhances crystallinity and passivates the grain boundary of the perovskite films. The stretchable PSCs with s-PU deliver a stabilized efficiency of 19.15 % with negligible hysteresis, which is comparable to the performance on rigid substrates. The PSCs can maintain over 90 % of their initial efficiency after 3000â hours in air because of their self-encapsulating structure. Importantly, the self-healing function of the s-PU scaffold was verified inâ situ. The s-PU can release mechanical stress and repair cracks at the grain boundary on multiple levels. The devices recover 88 % of their original efficiency after 1000â cycles at 20 % stretch. We believe that this ingenious growth strategy for crystalline semiconductors will facilitate development of flexible and stretchable electronics.
The blossoming of organic solar cells (OSCs) has triggered enormous commercial applications, due to their high-efficiency, light weight, and flexibility. However, the lab-to-manufacturing translation of the praisable performance from lab-scale devices to industrial-scale modules is still the Achilles' heel of OSCs. In fact, it is urgent to explore the mechanism of morphological evolution in the bulk heterojunction (BHJ) with different coating/printing methods. Here, a general approach to upscale flexible organic photovoltaics to module scale without obvious efficiency loss is demonstrated. The shear impulse during the coating/printing process is first applied to control the morphology evolution of the BHJ layer for both fullerene and nonfullerene acceptor systems. A quantitative transformation factor of shear impulse between slot-die printing and spin-coating is detected. Compelling results of morphological evolution, molecular stacking, and coarse-grained molecular simulation verify the validity of the impulse translation. Accordingly, the efficiency of flexible devices via slot-die printing achieves 9.10% for PTB7-Th:PC71 BM and 9.77% for PBDB-T:ITIC based on 1.04 cm2 . Furthermore, 15 cm2 flexible modules with effective efficiency up to 7.58% (PTB7-Th:PC71 BM) and 8.90% (PBDB-T:ITIC) are demonstrated with satisfying mechanical flexibility and operating stability. More importantly, this work outlines the shear impulse translation for organic printing electronics.
The application of metal grids as flexible transparent electrodes (FTEs) in optoelectronic devices is significantly influenced by poor adhesion and thickness difference between the metal and the substrate, resistance distribution uniformity, and a high annealing temperature. Direct inkjet printing of the metal mesh can overcome junction resistance while maintaining high conductivity, but the metal mesh thickness is still unsatisfactory. In addition, inkjet printing of mechanically durable metal FTEs directly on flexible substrates is challenging because of the high-temperature sintering treatment. Electroless deposition is a well-established method for low-cost and large-scale deposition of metal films. Here, ultrathin and ultraflexible Ag mesh@polydopamine (PDA)/poly(ethylene terephthalate) (PET) FTEs were fabricated by integrating inkjet-printed polymer matrices on a PDA-modified flexible PET substrate to form consecutive patterns as a mask and performing subsequent electroless deposition of the Ag mesh. The FTEs exhibit an excellent sheet resistance (Rs) of 9 Ω/sq with 89.9% transmittance. The resultant polymer solar cells show a superior power conversion efficiency (PCE) of 10.24% with 1 cm2 area and feature excellent flexural endurance (81% of initial PCE after 1500 bending cycles) and operational reliability (83% of initial PCE after 30 days). This ecofriendly and large-area fabrication technique has potential for future commercial applications of wearable electronics.
