High‐quality perovskite monocrystalline films are successfully grown through cavitation‐triggered asymmetric crystallization. These films enable a simple cell structure, ITO/CH3NH3PbBr3/Au, with near ...100% internal quantum efficiency, promising power conversion efficiencies (PCEs) >5%, and superior stability for prototype cells. Furthermore, the monocrystalline devices using a hole‐transporter‐free structure yield PCEs ≈6.5%, the highest among other similar‐structured CH3NH3PbBr3 solar cells to date.
Two dimensional layered organic-inorganic hybrid perovskites (2D perovskites) are potential candidates for next generation photovoltaic device. Especially, the out-of-plane surface perpendicular to ...the superlattice plane of 2D perovskites (layer-edge surface) has presented several exotic behaviors, such as layer-edge states which are found to be crucial for improving the efficiency of 2D perovskite solar cells. However, fundamental research on transport properties of layer-edge surface is still absent. In this report, we observe the electronic and opto-electronic behavior in layer-edge device of 2D perovskites. The dark and photo currents are demonstrated to strongly depend on the crystallographic orientation in layer-edge device, and such anisotropic properties, together with photo response, are related to the thickness of inorganic layers. Finally, due to the abundant hydroxyl groups, water molecules are easy to condense on the layer-edge surface, and the conductance is extremely sensitive to the humidity environment, indicating a potential application of humidity sensor.
Flexible and self‐powered photodetectors (PDs) are highly desirable for applications in image sensing, smart building, and optical communications. In this paper, a self‐powered and flexible PD based ...on the methylammonium lead iodide (CH3NH3PBI3) perovskite is demonstrated. Such a self‐powered PD can operate even with irregular motion such as human finger tapping, which enables it to work without a bulky external power source. In addition, with high‐quality CH3NH3PBI3 perovskite thin film fabricated with solvent engineering, the PD exhibits an impressive detectivity of 1.22 × 1013 Jones. In the self‐powered voltage detection mode, it achieves a large responsivity of up to 79.4 V mW−1 cm−2 and a voltage response of up to ≈90%. Moreover, as the PD is made of flexible and transparent polymer films, it can operate under bending and functions at 360 ° of illumination. As a result, the self‐powered, flexible, 360 ° omnidirectional perovskite PD, featuring high detectivity and responsivity along with real‐world sensing capability, suggests a new direction for next‐generation optical communications, sensing, and imaging applications.
A flexible and self‐powered organometallic halide perovskite photodetector is demonstrated that features an impressive detectivity of 1.22 × 1013 Jones and a large responsivity of up to 79.4 V mW−1 cm2. These results demonstrate a promising approach for developing a flexible and self‐powered photodetector featuring high detectivity, responsivity, and excellent compatibility in various situations, particularly for outdoor applications.
In the last half-century, the development of biodegradable polymeric materials for biomedical applications has advanced significantly. Biodegradable polymeric materials are favored in the development ...of therapeutic devices, including temporary implants and three-dimensional scaffolds for tissue engineering. Further advancements have occurred in the utilization of biodegradable polymeric materials for pharmacological applications such as delivery vehicles for controlled/sustained drug release. These applications require particular physicochemical, biological, and degradation properties of the materials to deliver effective therapy. As a result, a wide range of natural or synthetic polymers able to undergo hydrolytic or enzymatic degradation is being studied for biomedical applications. This review outlines the current development of biodegradable natural and synthetic polymeric materials for various biomedical applications, including tissue engineering, temporary implants, wound healing, and drug delivery.
Despite the remarkable progress of optoelectronic devices based on hybrid perovskites, there are significant drawbacks, which have largely hindered their development as an alternative of silicon. For ...instance, hybrid perovskites are well‐known to suffer from moisture instability which leads to surface degradation. Nonetheless, the dependence of the surface effect on the moisture stability and optoelectronic properties of hybrid perovskites has not been fully investigated. In this work, the influence of the surface effect of 2D layered perovskites before and after mechanical exfoliation, representing rough and smooth surfaces of perovskite crystals, are studied. It is found that the smooth 2D perovskite is less sensitive to ambient moisture and exhibits a considerably low dark current, which outperforms the rough perovskites by 23.6 times in terms of photodetectivity. The superior moisture stability of the smooth perovskites over the rough perovskites is demonstrated. Additionally, ethanolamine is employed as an organic linker of the 2D layered perovskite, which further improves the moisture stability. This work reveals the strong dependence of the surface conditions of 2D hybrid perovskite crystals on their moisture stability and optoelectronic properties, which are of utmost importance to the design of practical optoelectronic devices based on hybrid perovskite crystals.
The influence of the surface effect of 2D layered perovskites before and after mechanical exfoliation is studied. The smooth 2D perovskite is less sensitive to ambient moisture and exhibits a considerably low dark current. This work reveals the strong dependence of the surface condition of 2D hybrid perovskite crystals on their moisture stability and optoelectronic properties.
A facile yet effective surface modification strategy for superhydrophilicity and underwater superoleophobicity was developed by silanization of zwitterionic sulfobetaine silane (SBSi) on oxidized ...surfaces. The coatings exhibit excellent wetting properties, as indicated by static contact angles of <5°, and long-term stability under exposure to heat and UV irradiation. The SBSi-modified surfaces were employed for applications in antifog, self-cleaning, and oil–water separation. The SBSi glasses retained their optical transmittance because of the rapid formation of coalesced water thin films on surfaces in contact with water vapor and moisture. In addition, the underwater–oil contact-angle measurements verified the underwater superoleophobicity of the zwitterionic SBSi coatings. The oil spills on the SBSi coating could be readily removed in contact with water to realize the self-cleaning property. Besides, we modified stainless steel wire meshes with SBSi for oil–water separation. The optimal oil recovery rate for the oil–water mixtures reached >99.5% when using the SBSi-coated meshes with a pore size of 17 μm. More importantly, the water flux with modified meshes achieved 6.5 × 107 L/m2·h·bar, enabling gravity-driven and energy-saving separation. Consequently, we demonstrated the superhydrophilicity and underwater superoleophobicity of SBSi, offering promise in solving technological problems of interfacial fog, oil spills, and oil–water separation and thereby showing great potential in large-scale commercial applications.
Unintentional self-doping in semiconductors through shallow defects is detrimental to optoelectronic device performance. It adversely affects junction properties and it introduces electronic noise. ...This is especially acute for solution-processed semiconductors, including hybrid perovskites, which are usually high in defects due to rapid crystallization. Here, we uncover extremely low self-doping concentrations in single crystals of the two-dimensional perovskites (C6H5C2H4NH3)2PbI4·(CH3NH3PbI3) n−1 (n = 1, 2, and 3), over three orders of magnitude lower than those of typical three-dimensional hybrid perovskites, by analyzing their conductivity behavior. We propose that crystallization of hybrid perovskites containing large organic cations suppresses defect formation and thus favors a low self-doping level. To exemplify the benefits of this effect, we demonstrate extraordinarily high light-detectivity (1013 Jones) in (C6H5C2H4NH3)2PbI4·(CH3NH3PbI3) n−1 photoconductors due to the reduced electronic noise, which makes them particularly attractive for the detection of weak light signals. Furthermore, the low self-doping concentration reduces the equilibrium charge carrier concentration in (C6H5C2H4NH3)2PbI4·(CH3NH3PbI3) n−1, advantageous in the design of p–i–n heterojunction solar cells by optimizing band alignment and promoting carrier depletion in the intrinsic perovskite layer, thereby enhancing charge extraction.
Amid growing interest in using body heat for electricity in wearables, creating stretchable devices poses a major challenge. Herein, a hydrogel composed of two core constituents, namely the ...negatively‐charged 2‐acrylamido‐2‐methylpropanesulfonic acid and the zwitterionic (ZI) sulfobetaine acrylamide, is engineered into a double‐network hydrogel. This results in a significant enhancement in mechanical properties, with tensile stress and strain of up to 470.3 kPa and 106.6%, respectively. Moreover, the ZI nature of the polymer enables the fabrication of a device with polar thermoelectric properties by modulating the pH. Thus, the ionic Seebeck coefficient (Si) of the ZI hydrogel ranges from −32.6 to 31.7 mV K−1 as the pH is varied from 1 to 14, giving substantial figure of merit (ZTi) values of 3.8 and 3.6, respectively. Moreover, a prototype stretchable ionic thermoelectric supercapacitor incorporating the ZI hydrogel exhibits notable power densities of 1.8 and 0.9 mW m−2 at pH 1 and 14, respectively. Thus, the present work paves the way for the utilization of pH‐sensitive, stretchable ZI hydrogels for thermoelectric applications, with a specific focus on harvesting low‐grade waste heat within the temperature range of 25–40 °C.
Combining p‐type and n‐type devices is an approach to enhance ionic thermoelectric properties. Herein, a pH‐sensitive zwitterionic hydrogel achieves bipolar thermoelectric performance, with a Seebeck coefficient of −32.6 to 31.7 mV K−1 at pH 1 and 14. Research into controlled pH values opens avenues for advancing the bipolar Seebeck coefficient in ionic thermoelectric supercapacitors, highlighting promising possibilities in the field.
This work presents a salt-responsive interpenetrating network (IPN) hydrogel with effective antimicrobial properties and surface regeneration. The hydrogels were engineered using the double network ...strategy to form loosely cross-linked zwitterionic poly(sulfobetaine vinylimidazole) (pSBVI) networks into the highly cross-linked cationic poly((trimethylamino)ethyl methacrylate chloride) (pTMAEMA) framework via photopolymerization. The pTMAEMA/pSBVI hydrogel has strong mechanical properties, with a fracture stress 120× higher than single network pTMAEMA hydrogel. In addition, there is inverse correlation between elastic modulus and elastic strain of pTMAEMA/pSBVI hydrogels as a function of ionic strength. The cationic pTMAEMA and zwitterionic pSBVI show opposite swelling behaviors in salt solutions due to the polyelectrolyte effect and antipolyelectrolyte effect. Therefore, the pTMAEMA/pSBVI hydrogel elicits a significant interfacial transition in solutions with different ionic strengths. The IPN hydrogels have switchable lubrication and optical transmittance between deionized water and 1.0 M NaCl solution. The protein adsorption tests further confirmed the switchable interface of salt-responsive IPN hydrogels. In addition, bacterial attachment test on pTMAEMA/pSBVI hydrogels with Staphylococcus epidermidis (S. epidermidis) and Escherichia coli (E. coli) show bacterial killing rates of the IPN hydrogel over 80% for S. epidermidis and 90% for E. coli after incubating the hydrogels in the bacterial solutions for 24 h. The bacterial release rate from the IPN hydrogel reached 96% after washing with 1.0 M NaCl solution. Furthermore, the excellent reusability of the pTMAEMA/pSBVI hydrogels was demonstrated by the high bacterial killing and bacterial release rates after five kill/release cycles. The work presents a new stimuli-responsive IPN hydrogel with structural modulation, tunable antimicrobial properties, and surface regeneration by ionic strength. Integrating two salt-responsive polymers with mutually independent actions into a single material provides a new direction for smart materials with potential medical and industrial applications.
Bone morphogenetic protein-2 (BMP-2) is currently the only Food and Drug Administration (FDA)-approved osteoinductive growth factor used as a bone graft substitute. However, with increasing clinical ...use of BMP-2, a growing and well-documented side effect profile has emerged. This includes postoperative inflammation and associated adverse effects, ectopic bone formation, osteoclast-mediated bone resorption, and inappropriate adipogenesis. Several large-scale studies have confirmed the relative frequency of adverse events associated with the clinical use of BMP-2, including life-threatening cervical spine swelling. In fact, the FDA has issued a warning of the potential life-threatening complications of BMP-2. This review summarizes the known adverse effects of BMP-2, including controversial areas such as tumorigenesis. Next, select animal models that replicate BMP-2's adverse clinical effects are discussed. Finally, potential molecules to mitigate the adverse effects of BMP-2 are reviewed. In summary, BMP-2 is a potent osteoinductive cytokine that has indeed revolutionized the bone graft substitute market; however, it simultaneously has accrued a worrisome side effect profile. Better understanding of these adverse effects among both translational scientists and clinicians will help determine the most appropriate and safe use of BMP-2 in the clinical setting.
PDF
