Molecular Design and Operational Stability: Toward Stable 3D/2D Perovskite Interlayers

3D Bioprinted Xanthan Hydrogels with Dual Antioxidant and Chondrogenic Functions for Post-traumatic Cartilage Regeneration

Intra-articular trauma typically initiates the overgeneration of reactive oxidative species (ROS), leading to post-traumatic osteoarthritis and cartilage degeneration. Xanthan gum (XG), a branched polysaccharide, has shown its potential in many biomedical fields, but some of its inherent properties, including undesirable viscosity and poor mechanical stability, limit its application in 3D printed scaffolds for cartilage regeneration. In this project, we developed 3D bioprinted XG hydrogels by modifying XG with methacrylic (MA) groups for post-traumatic cartilage therapy. Our results demonstrated that the chemical modification optimized the viscoelasticity of the bioink, improved printability, and enhanced the mechanical properties of the resulting scaffolds. The XG hydrogels also exhibit decent ROS scavenging capacities to protect stem cells from oxidative stress. Furthermore, XGMA(H) (5% MA substitution) exhibited superior chondrogenic potential in vitro and promoted cartilage regeneration in vivo. These dual-functional XGMA hydrogels may provide a new opportunity for cartilage tissue engineering.

Long-chain organic molecules enable mixed dimensional perovskite photovoltaics: a brief view

The remarkable optoelectronic properties of organometal halide perovskite solar cells have captivated significant attention in the energy sector. Nevertheless, the instability of 3D perovskites, despite their extensive study and attainment of high-power conversion efficiency, remains a substantial obstacle in advancing PSCs for practical applications and eventual commercialization. To tackle this issue, researchers have devised mixed-dimensional perovskite structures combining 1D and 3D components. This innovative approach entails incorporating stable 1D perovskites into 3D perovskite matrices, yielding a significant improvement in long-term stability against various challenges, including moisture, continuous illumination, and thermal stress. Notably, the incorporation of 1D perovskite yields a multitude of advantages. Firstly, it efficiently passivates defects, thereby improving the overall device quality. Secondly, it retards ion migration, a pivotal factor in degradation, thus further bolstering stability. Lastly, the inclusion of 1D perovskite facilitates charge transport, ultimately resulting in an elevated device efficiency. In this succinct review, we thoroughly encapsulate the recent progress in PSCs utilizing 1D/3D mixed-dimensional architectures. These advancements encompass both stacked bilayer configurations of 1D/3D structures and mixed monolayer structures of 1D/3D. Additionally, we tackle critical challenges that must be surmounted and offer insights into the prospects for further advancements in this domain.

Improved 3D-2D Perovskite for Efficient Perovskite Photovoltaics with Low-Temperature Carbon Electrodes

Surface passivation and interface modification are effective strategies to acquire outstanding performances for perovskite solar cells (PeSCs). To suppress charge recombination and enhance the stability of the perovskite device, a hydrophobic two-dimensional (2D) perovskite is presented to construct a 3D-2D composite perovskite, passivating the perovskite surface/interfacial imperfection. Herein, a 3D-2D heterojunction perovskite is in situ synthesized on a 3D surface to maximize the charge transport and environmental stability. Through optimizing the annealing procedure systematically, the champion 3D-2D carbon-based PeSC achieves a power conversion efficiency of 17.95% and has wonderful long-term stability. Especially, an improved 3D-2D (3D-2D+) PeSC from restrict annealing even maintains 96.2% of the initial efficiency in air over 800 h and 90% efficiency under continuous 70 °C heating for 10 h owing to the passivation of the surface and thorough crystal boundary for the 3D-2D+ perovskite. The strong environmental stability of 3D-2D PeSCs has provided a wider avenue for fully low-temperature carbon-based PeSCs.

Energy Level Matching and Band Edge Reconfiguration for Enhanced Charge Transport in Dion-Jacobson 3D/2D Perovskite Heterojunctions

Generally, the 2D CsPbI₃ layer capping on 3D counterparts has been considered as an effective strategy for both enhancing photovoltaic efficiency and stability. However, the intrinsically poor out-of-plane charge transport through the 2D layer remarkably hinders the overall performance of solar devices. To overcome such a challenge, we report the rationally designed 3D-CsPbI₃/2D-(PY_n)PbI₄ (n = 1-4) heterojunctions with desirable energy level matching. It is evidenced that the valence band (VB) edge reconfiguration would occur with the increase of n, accompanied by the VB maximum (VBM) of the 2D component moving down from the higher level above that of the 3D component to the underneath. Consequently, the as-constructed 3D/2D-(PY_n)PbI₄ (n = 1, 2) heterojunctions exhibit optimal energy level matching, with accelerated transport of holes from 3D to 2D component and limited backflow of electrons. These findings might provide some meaningful insights on the energy level matching in 3D/2D perovskite heterojunctions.

Influence of the Alkyl Chain Length of (Pentafluorophenylalkyl) Ammonium Salts on Inverted Perovskite Solar Cell Performance

We study the effect of (2,3,4,5,6-pentafluorophenyl)alkylamine additives with differing alkyl chain lengths (methyl, ethyl, and n-propyl) on the performance of methylammonium lead triiodide (MAPbI₃) perovskite solar cells. The results show that the length of the alkyl chain between the 2,3,4,5,6-pentafluorophenyl group and ammonium moiety has a critical effect on the perovskite film structure and subsequent device performance. The 2,3,4,5,6-pentafluorophenyl ammonium additive with the shortest linking group (a methylene unit), namely (2,3,4,5,6-pentafluorophenyl)methylammonium iodide, was found to be distributed throughout the bulk of the perovskite film with a 2D phase only being observable at high concentrations (>30 mol%). In contrast, the additives with ethyl and n-propyl linking groups phase-separate during solution processing and are found to concentrate at the surface of the perovskite film. Photoluminescence measurements showed that the fluorinated additives passivated the surface defects on the perovskite grains. Of the three additives, inverted devices containing 0.32 mol% of the 2,3,4,5,6-pentafluorophenyl ammonium additive with the methylene linking group achieved a maximum power conversion efficiency of 22.0%, with the device efficiency decreasing with increasing additive concentration. In contrast, the devices composed of the additive with the longest alkyl linker, 3-(2,3,4,5,6-pentafluorophenyl)propylammonium iodide, had the poorest performance, with PCEs less than that of the neat MAPbI₃ control and decreasing with increasing additive concentration.

Highly Efficient and Stable 2D Dion Jacobson/3D Perovskite Heterojunction Solar Cells

Heterostructures involving two-dimensional/three-dimensional (2D/3D) perovskites have recently attracted increased attention due to their ability to combine the high photovoltaic performance of 3D perovskites with the increased stability of 2D perovskites. Here we report ammonium thiocyanate (NH₄SCN) passivated 3D methylammonium lead triiodide (MAPbI₃) perovskite active layer and deposition of 2D perovskite capping layer using xylylene diammonium iodide (XDAI) organic cation. The 2D/3D perovskite heterojunction formation is probed by using FESEM and UPS spectroscopy. The NH₄SCN passivated MAPbI₃ perovskite has shown 19.6% PCE compared to the 17.18% PCE of pristine MAPbI₃ perovskite solar cells (PSCs). Finally, the champion 2D/3D perovskite heterojunction based solar cells have achieved the remarkable PCE of 20.74%. The increased PCE in 2D/3D PSCs is mainly attributed to the reduced defect density and suppressed nonradiative recombination losses. Moreover, the hydrophobic 2D capping layer endows the 2D/3D heterojunction perovskites with exceptional moisture, thermal and UV stability, highlighting the promise of highly stable and efficient 2D/3D PSCs.

From Structural Design to Functional Construction: Amine Molecules in High-Performance Formamidinium-Based Perovskite Solar Cells

Formamidinium (FA) based perovskites are considered as one of the most promising light-absorbing perovskite materials owing to their narrower band gap and better thermal stability compared to conventional methylammonium-based perovskites. Constant improvement by using various additives stimulates the potential application of these perovskites. Amine molecules with different structures have been widely used as typical additives in FA-based perovskite solar cells, and decent performances have been achieved. Thus, a systematic review focusing on structural regulation and functional construction of amines in FA-based perovskites is of significance. Herein, we analyze the construction mechanism of different structural amines on the functional perovskite crystals. The influence of amine molecules on specific perovskite properties including defect conditions, charge transfer, and moisture resistance are evaluated. Finally, we summarize the design rules of amine molecules for the application in high-performance FA-based perovskites and propose directions for the future development of additive molecules.

Halogen hydrogen-bonded organic framework (XHOF) constructed by singlet open-shell diradical for efficient photoreduction of U(VI)

Synthesis of framework materials possessing specific spatial structures or containing functional ligands has attracted tremendous attention. Herein, a halogen hydrogen-bonded organic framework (XHOF) is fabricated by using Cl- ions as central connection nodes to connect organic ligands, 7,7,8,8-tetraaminoquinodimethane (TAQ), by forming a Cl-···H3 hydrogen bond structure. Unlike metallic node-linked MOFs, covalent bond-linked COFs, and intermolecular hydrogen bond-linked HOFs, XHOFs represent a different kind of crystalline framework. The electron-withdrawing effect of Cl- combined with the electron-rich property of the organic ligand TAQ strengthens the hydrogen bonds and endows XHOF-TAQ with high stability. Due to the production of excited electrons by TAQ under light irradiation, XHOF-TAQ can efficiently catalyze the reduction of soluble U(VI) to insoluble U(IV) with a capacity of 1708 mg-U g-1-material. This study fabricates a material for uranium immobilization for the sustainability of the environment and opens up a new direction for synthesizing crystalline framework materials.

Halogen Bonding in Perovskite Solar Cells: A New Tool for Improving Solar Energy Conversion

Hybrid organic–inorganic halide perovskites (HOIHPs) have recently emerged as a flourishing area of research. Their easy and low‐cost production and their unique optoelectronic properties make them promising materials for many applications. In particular, HOIHPs hold great potential for next‐generation solar cells. However, their practical implementation is still hindered by their poor stability in air and moisture, which is responsible for their short lifetime. Optimizing the chemical composition of materials and exploiting non‐covalent interactions for interfacial and defects engineering, as well as defect passivation, are efficient routes towards enhancing the overall efficiency and stability of perovskite solar cells (PSCs). Due to the rich halogen chemistry of HOIHPs, exploiting halogen bonding, in particular, may pave the way towards the development of highly stable PSCs. Improved crystallization and stability, reduction of the surface trap states, and the possibility of forming ordered structures have already been preliminarily demonstrated.

Diammonium Molecular Configuration-Induced Regulation of Crystal Orientation and Carrier Dynamics for Highly Efficient and Stable 2D/3D Perovskite Solar Cells

The effects from the molecular configuration of diammonium spacer cations on 2D/3D perovskite properties are still unclear. Here, we investigated systematically the mechanism of molecular configuration-induced regulation of crystallization kinetic and carrier dynamics by employing various diammonium molecules to construct Dion-Jacobson (DJ)-type 2D/3D perovskites to further facilitating the photovoltaic performance. The minimum average Pb-I-Pb angle leads to the smallest octahedral tilting of [PbX₆ ]^4- lattice in optimal diammonium molecule-incorporated DJ-type 2D/3D perovskite, which enables suitable binding energy and hydrogen-bonding between spacer cations and inorganic [PbX₆ ]^4- cages, thus contributing to the formation of high-quality perovskite film with vertical crystal orientation, mitigatory lattice distortion and efficient carrier transportation. As a consequence, a dramatically improved device efficiency of 22.68 % is achieved with excellent moisture stability.

Tuning structural isomers of phenylenediammonium to afford efficient and stable perovskite solar cells and modules

Organic halide salt passivation is considered to be an essential strategy to reduce defects in state-of-the-art perovskite solar cells (PSCs). This strategy, however, suffers from the inevitable formation of in-plane favored two-dimensional (2D) perovskite layers with impaired charge transport, especially under thermal conditions, impeding photovoltaic performance and device scale-up. To overcome this limitation, we studied the energy barrier of 2D perovskite formation from ortho-, meta- and para-isomers of (phenylene)di(ethylammonium) iodide (PDEAI₂) that were designed for tailored defect passivation. Treatment with the most sterically hindered ortho-isomer not only prevents the formation of surficial 2D perovskite film, even at elevated temperatures, but also maximizes the passivation effect on both shallow- and deep-level defects. The ensuing PSCs achieve an efficiency of 23.9% with long-term operational stability (over 1000 h). Importantly, a record efficiency of 21.4% for the perovskite module with an active area of 26 cm² was achieved.