Engineering Interfacial Built-in Electric Field in Polymetallic Phosphide Heterostructures for Superior Supercapacitors and Electrocatalytic Hydrogen Evolution.

Herein, a patterned rod-like CoP@NiCoP core-shell heterostructure is designed to consist of CoP nanowires cross-linked with NiCoP nanosheets in tight strings. The interfacial interaction within the heterojunction between the two components generates a built-in electric field that adjusts the interfacial charge state and create more active sites, accelerating the charge transfer and improving supercapacitor and electrocatalytic performance. The unique core-shell structure suppresses the volume expansion during charging and discharging, achieving excellent stability. As a result, CoP@NiCoP exhibits a high specific capacitance of 2.9 F cm-2 at a current density of 3 mA cm-2 and a high ion diffusion rate (Dion is 2.95 × 10-14  cm2  s-1 ) during charging/discharging. The assembled asymmetric supercapacitor CoP@NiCoP//AC exhibits a high energy density of 42.2 Wh kg-1 at a power density of 126.5 W kg-1 and excellent stability with a capacitance retention rate of 83.8% after 10 000 cycles. Furthermore, the modulated effect induced by the interfacial interaction also endows the self-supported electrode with excellent electrocatalytic HER performance with an overpotential of 71 mV at 10 mA cm-2 . This research may provide a new perspective on the generation of built-in electric field through the rational design of heterogeneous structures for improving the electrochemical and electrocatalytical performance.

Asymmetrically Substituted 10H,10'H-9,9'-Spirobi[acridine] Derivatives as Hole-Transporting Materials for Perovskite Solar Cells.

Hole-transporting materials (HTMs) based on the 10H, 10'H-9,9'-spirobi [acridine] core (BSA50 and BSA51) were synthesized, and their electronic properties were explored. Experimental and theoretical studies show that the presence of rigid 3,6-dimethoxy-9H-carbazole moieties in BSA 50 brings about improved hole mobility and higher work function compared to bis(4-methoxyphenyl)amine units in BSA51, which increase interfacial hole transportation from perovskite to HTM. As a result, perovskite solar cells (PSCs) based on BSA50 boost power conversion efficiency (PCE) to 22.65 %, and a PSC module using BSA50 HTM exhibits a PCE of 21.35 % (6.5×7 cm) with a Voc of 8.761 V and FF of 79.1 %. The unencapsulated PSCs exhibit superior stability to devices employing spiro-OMeTAD, retaining nearly 90 % of their initial efficiency after 1000 h operation output. This work demonstrates the high potential of molecularly engineered spirobi[acridine] derivatives as HTMs as replacements for spiro-OMeTAD.

Hexylammonium Acetate-Regulated Buried Interface for Efficient and Stable Perovskite Solar Cells.

Due to current issues of energy-level mismatch and low transport efficiency in commonly used electron transport layers (ETLs), such as TiO2 and SnO2, finding a more effective method to passivate the ETL and perovskite interface has become an urgent matter. In this work, we integrated a new material, the ionic liquid (IL) hexylammonium acetate (HAAc), into the SnO2/perovskite interface to improve performance via the improvement of perovskite quality formed by the two-step method. The IL anions fill oxygen vacancy defects in SnO2, while the IL cations interact chemically with Pb2+ within the perovskite structure, reducing defects and optimizing the morphology of the perovskite film such that the energy levels of the ETL and perovskite become better matched. Consequently, the decrease in non-radiative recombination promotes enhanced electron transport efficiency. Utilizing HAAc, we successfully regulated the morphology and defect states of the perovskite layer, resulting in devices surpassing 24% efficiency. This research breakthrough not only introduces a novel material but also propels the utilization of ILs in enhancing the performance of perovskite photovoltaic systems using two-step synthesis.

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.

Foldable Hole-Transporting Materials for Merging Electronic States between Defective and Perfect Perovskite Sites.

Defective and perfect sites naturally exist within electronic semiconductors, and considerable efforts to reduce defects to improve the performance of electronic devices, especially in hybrid organic-inorganic perovskites (ABX3 ), are undertaken. Herein, foldable hole-transporting materials (HTMs) are developed, and they extend the wavefunctions of A-site cations of perovskite, which, as hybridized electronic states, link the trap states (defective site) and valence band edge (perfect site) between the naturally defective and perfect sites of the perovskite surface, finally converting the discrete trap states of the perovskite as the continuous valence band to reduce trap recombination. Tailoring the foldability of the HTMs tunes the wavefunctions between defective and perfect surface sites, allowing the power conversion efficiency of a small cell to reach 23.22% and that of a mini-module (6.5 × 7 cm, active area = 30.24 cm2 ) to reach as high as 21.71% with a fill factor of 81%, the highest value reported for non-spiro-OMeTAD-based perovskite solar modules.

Coupling water cycle processes with water demand routes of vegetation using a cascade causal modeling approach in arid inland basins.

Vegetation degradation is the key cause of land desertification in arid areas. Water stress is one of the most critical factors leading to vegetation degradation. The water needed for vegetation growth is inseparable from the water cycle processes. It is a new scope to reveal the vegetation water demand mechanisms from the water cycle processes. Water cycle processes in arid inland basins can be conceptually separated as RFA (runoff formation area) and RCA (runoff consumption area). In this study, both the water demand mechanisms of natural vegetation and farmland were discovered by creatively constructing the vegetation water demand route model. The TRB (Tarim River Basin), a typical arid inland basin system that RFA is separated from RCA, is considered as the study area. The tendency and relevance of water cycle factors and NDVI were detected. The dominant factors of vegetation growth were identified. According to the interaction causality of water cycle factors and vegetation, the PLS-SEM (partial least squares structural equation models) were constructed in RFA and RCA. Results displayed that SMroot (root-zone soil moisture), groundwater and precipitation were the dominant water sources for natural vegetation in RFA. The water demand for natural vegetation in RCA mainly came from SMroot and that for farmland mainly came from SMsurf (surface soil moisture). New findings showed that blue and green water circulations were more active in RFA than in RCA. Natural vegetation had better adaptability and resilience to water shortages compared with farmland. The higher effect of vegetation on AET (actual evapotranspiration) denoted the better growth status. It is contributed to the rational utilization of water resources in arid basins.

Internal Interactions between Mixed Bulky Organic Cations on Passivating Defects in Perovskite Solar Cells.

In perovskite solar cells (PSCs), bulky organic cation halide salt additions play a significant role in suppressing nonradiative recombination by passivating intrinsic defects in perovskites. Herein, a passivation treatment is developed by applying mixed bulky cations [guanidinium cation (GA+) and phenylethylammonium cations (PEA+)] as the additive for perovskite thin films. The internal interactions between the two bulky cations could result in lower carrier trap-state densities, a sharper Urbach tail, and better carrier transport in perovskite films in comparison with a control film. As a result, in comparison to the control device, which has a power conversion efficiency (PCE) of 18.92%, the mixed-cation-based device exhibits a dramatic enhancement of PCE of 20.64%. Importantly, after 720 h of storage in an ambient atmosphere with a relative humidity (RH) of 60-80% at room temperature, the mixed-cation-based device retains 62.7% of its original performance, whereas the control devices decay to less than 40% of their original performance.

Perfection of Perovskite Grain Boundary Passivation by Rhodium Incorporation for Efficient and Stable Solar Cells.

Organic cation and halide anion defects are omnipresent in the perovskite films, which will destroy perovskite electronic structure and downgrade the properties of devices. Defect passivation in halide perovskites is crucial to the application of solar cells. Herein, tiny amounts of trivalent rhodium ion incorporation can help the nucleation of perovskite grain and passivate the defects in the grain boundaries, which can improve efficiency and stability of perovskite solar cells. Through first-principle calculations, rhodium ion incorporation into the perovskite structure can induce ordered arrangement and tune bandgap. In experiment, rhodium ion incorporation with perovskite can contribute to preparing larger crystalline and uniform film, reducing trap-state density and enlarging charge carrier lifetime. After optimizing the content of 1% rhodium, the devices achieved an efficiency up to 20.71% without obvious hysteresis, from 19.09% of that pristine perovskite. In addition, the unencapsulated solar cells maintain 92% of its initial efficiency after 500 h in dry air. This work highlights the advantages of trivalent rhodium ion incorporation in the characteristics of perovskite solar cells, which will promote the future industrial application.

Stable and High-Efficiency Methylammonium-Free Perovskite Solar Cells.

Organic-inorganic metal halide perovskite solar cells (PSCs) have achieved certified power conversion efficiency (PCE) of 25.2% with complex compositional and bandgap engineering. However, the thermal instability of methylammonium (MA) cation can cause the degradation of the perovskite film, remaining a risk for the long-term stability of the devices. Herein, a unique method is demonstrated to fabricate highly phase-stable perovskite film without MA by introducing cesium chloride (CsCl) in the double cation (Cs, formamidinium) perovskite precursor. Moreover, due to the suboptimal bandgap of bromide (Br- ), the amount of Br- is regulated, leading to high power conversion efficiency. As a result, MA-free perovskite solar cells achieve remarkable long-term stability and a PCE of 20.50%, which is one of the best results for MA-free PSCs. Moreover, the unencapsulated device retains about 80% of the original efficiencies after a 1000 h aging study. These results provide a feasible approach to enhance solar cell stability and performance simultaneously, paving the way for commercializing PSCs.

Enhancing the Performance of Inverted Perovskite Solar Cells via Grain Boundary Passivation with Carbon Quantum Dots.

Nonradiative recombination, the main energy loss channel for open circuit voltage ( Voc), is one of the crucial problems for achieving high power conversion efficiency (PCE) in inverted perovskite solar cells (PSCs). Usually, grain boundary passivation is considered as an effective way to reduce nonradiative recombination because the defects (uncoordinated ions) on grain boundaries are passivated. We added the hydroxyl and carbonyl functional groups containing carbon quantum dots (CQDs) into a perovskite precursor solution to passivate the uncoordinated lead ions on grain boundaries. Higher photoluminescence intensity and longer carrier lifetime were demonstrated in the perovskite film with the CQD additive. This confirmed that the addition of CQDs can reduce nonradiative recombination by grain boundary passivation. Additionally, the introduction of CQDs could increase the thickness of the perovskite film. Consequently, we achieved a champion device with a PCE of 18.24%. The device with CQDs retained 73.4% of its initial PCE after being aged for 48 h under 80% humidity in the dark at room temperature. Our findings reveal the mechanisms of how CQDs passivate the grain boundaries of perovskite, which can improve the efficiency and stability of PSCs.