Active Area Efficiency Research Articles

Revolutionizing CO2‐to‐C2 Conversion: Unleashing the Potential of CeO2 Nanocores for Self‐ Supported Electrocatalysts with Cu2O Nanoflakes on 3D Graphene Aerogel

AbstractCu serves as a promising electrocatalyst for converting CO2 into valuable C2 products in CO2 reduction reactions (CO2RR). However, instability in CO* formation is crucial for CO2 adsorption‐ desorption still remains a challenge under reduction conditions. This study explores the impact of lanthanide oxide, particularly CeO2, on Cu‐based catalytic performances. By leveraging Ce's distinctive electronic structure, CO* species are stabilized during the reaction in CeO2─Cu2O, resulting in exceptional catalytic performance for CO2 electroreduction to C2 products. Hybridizing CeO2‐Cu2O with graphene aerogel enhances electrochemical active surface area and CO2RR efficiency. The resulting CeO2─Cu2O(10%)/GA electrocatalyst exhibits a remarkable faradaic efficiency for C2 products, exceeding 62%, alongside exceptional stability over 80 h with wide potential window (−0.8 to −1.2 V) using a H‐cell. Systematic investigations elucidate the intricate interplay between surface properties and catalytic activity. Furthermore, a solar cell‐ powered CO2 reduction system demonstrates consistent performance (−27.8 mA cm−2 at 3.46 V) under solar radiation of ≈100 mW cm−2, showcasing outstanding stability with nearly 100% retention over 4 h of continuous illumination. In short, by harnessing catalytic and electronic effects, this innovation advances the development of electrocatalysts with heightened CO2‐to‐C2 selectivity, bridging fundamental research with technological innovation to tackle critical global challenges.

Stabilizing Solution–Substrate Interaction of Perovskite Ink on PEDOT:PSS for Scalable Blade Coated Narrow Bandgap Perovskite Solar Modules by Gas Quenching

The development of scalable 1.25 eV mixed Pb–Sn perovskite solar modules by blade coating lags behind Pb‐based perovskites due to limited understanding of solution–substrate interaction of the perovskite ink on PEDOT:PSS and subsequent gas quenching. To address this challenge, the wet film deposition and quenching process to better understand narrow bandgap perovskite film formation on PEDOT:PSS are studied. It is found that the wetting of Pb–Sn perovskite ink on PEDOT:PSS is highly unstable over relevant coating time scales, causing the contact angles to decrease rapidly from 42° to 16° within seconds. This instability leads to localized irregularities in the wet film, resulting in uneven solvent extraction and inhomogeneous nuclei density. As a result, rough perovskite films with voids at the buried interface are obtained. To overcome this problem, a quasistatic wetting process by reducing the blade coating speed is developed, thereby stabilizing the wetting behavior of Pb–Sn perovskite precursor ink on PEDOT:PSS. This optimized process facilitates the deposition of high‐quality, void‐free Pb–Sn perovskite films with uniform thickness over 8 cm of coating length using moderate (1.4 bar) N2 quenching. 20% efficient narrow bandgap perovskite solar cells and minimodules with 15.8% active area efficiency on 15.9 cm2 are achieved.

Petal-by-petal tree-blossoming shaped bimetallic MOF-based material over SBA-15: Diverse designability, synergistic catalysis, and thermodynamics/kinetic analysis

Transition metal-based bimetallic MOF (CoMo-ZIF) with two different metal ions (Co/Mo) possess specific synergistic catalytic effect in olefins oxidation, but poor diffusion efficiency and less active areas limit its application. Herein, a novel CoMo-ZIF-based nanocomposite is fabricated via an in-situ solvothermal approach to break down active area or diffusion efficiency barrier of CoMo-ZIF via employing SBA-15 as the matrix and nanosacle polyoxometalate (POM) as external active species. Characterizations reveal that pristine rose-type CoMo-ZIF (∼350 nm diameter) alters to rambutan-like hollow sphere and eventually self-assembles into hierarchical petal-by-petal nanoflakes (ca. 20∼50 nm in thickness) after SBA-15 and POM introduction, respectively. POM@CoMo-ZIF@SBA-15 with super large pore size (10.44 nm) and increased active (Co2+ + Co3+)/satellite (1.92) exhibits excellent catalytic activity in cyclopentene (CPE) oxidation to glutaric acid (GAC) with 57.1 % CCPE, 61.6 % SGAC, and good reusability with 54.3∼57.1 % CCPE and 58.4∼63.2 % SGAC during 6 cycles. What's more, thermodynamic analysis indicates that CPE oxidation to GAC is a spontaneous reaction at 273.15∼373.15 K, and kinetic study shows that the key to develop CPE to GAC is to reduce activation energies of cyclopentene oxide ring-opening to 1,2-cyclopentanediol (73.8298 kJ⋅mol−1) and glutaradehyde (118.4571 kJ⋅mol−1). This study not only pioneers a promising strategy for oriented design of MOF-based materials, but also serves as a valuable reference for the computation of various chemical reactions.

CuCo2O4 nanoneedle arrays growth on carbon cloth as a non-enzymatic electrochemical sensor with low detection limit ketoprofen recognition.

An electrochemical sensor for detecting ketoprofen was constructed by in-situ grown copper cobaltate (CuCo2O4) nanoneedle arrays on a carbon cloth (CC) substrate. The resulting porous nanoneedle arrays not only expose numerous electrochemically active sites but also significantly enhance the electrochemical apparent active area and current transmission efficiency. By leveraging its electrochemical properties, the sensor achieves an impressive detection limit for ketoprofen of0.7 pM, with a linear range spanning from 2 pM ~ 2 µM. Furthermore, the sensor exhibits remarkable reproducibility, anti-interference capabilities, and stability. Notably, the developed sensor also performed ketoprofen detection on real samples (including drug formulations and wastewater) and demonstrated excellent recognition ability. These exceptional performances can be attributed to the direct growth of CuCo2O4 nanoneedle arrays on the CC substrate, which facilitates a robust electrical connection, provides abundant electrocatalytic active sites, and expands the apparent active area. Consequently, these improvements contribute to the efficient trace detection capabilities of the ketoprofen sensor.

Dimensional Regulation from 1D/3D to 2D/3D of Perovskite Interfaces for Stable Inverted Perovskite Solar Cells.

Constructing low-dimensional/three-dimensional (LD/3D) perovskite solar cells can improve efficiency and stability. However, the design and selection of LD perovskite capping materials are incredibly scarce for inverted perovskite solar cells (PSCs) because LD perovskite capping layers often favor hole extraction and impede electron extraction. Here, we develop a facile and effective strategy to modify the perovskite surface by passivating the surface defects and modulating surface electrical properties by incorporating morpholine hydriodide (MORI) and thiomorpholine hydriodide (SMORI) on the perovskite surface. Compared with the PI treatment that we previously developed, the one-dimensional (1D) perovskite capping layer derived from PI is transformed into a two-dimensional (2D) perovskite capping layer (with MORI or SMORI), achieving dimension regulation. It is shown that the 2D SMORI perovskite capping layer induces more robust surface passivation and stronger n-N homotype 2D/3D heterojunctions, achieving a p-i-n inverted solar cell with an efficiency of 24.55%, which retains 87.6% of its initial efficiency after 1500 h of operation at the maximum power point (MPP). Furthermore, 5 × 5 cm2 perovskite mini-modules are presented, achieving an active-area efficiency of 22.28%. In addition, the quantum well structure in the 2D perovskite capping layer increases the moisture resistance, suppresses ion migration, and improves PSCs' structural and environmental stability.

Rear Surface Passivation for Ink‐Based, Submicron CuIn(S, Se)2 Solar Cells

AbstractA N, N‐dimethylformamide and thiourea‐based route is developed to fabricate submicron (0.55 and 0.75 µm) thick CuIn(S,Se)2 (CISSe) thin films for photovoltaic applications, addressing challenges of material usage, throughput, and manufacturing costs. However, reducing the absorber film thickness below 1 µm in a regular CISSe solar cell decreases the device efficiency due to losses at the highly‐recombinative, and mediocre‐reflective Mo/CISSe rear interface. For the first time, to mitigate the rear recombination losses, a novel rear contacting structure involving a surface passivation layer and point contact openings is developed for solution processed CISSe films and demonstrated in tangible devices. An atomic layer deposited Al2O3 film is employed to passivate the Mo/CISSe rear surface while precipitates formed via chemical bath deposition of CdS are used to generate nanosized point openings. Consequently, Al2O3 passivated CISSe solar cells show an increase in the open‐circuit voltage (VOC) and short‐circuit current density when compared to reference cells with equivalent absorber thicknesses. Notably, a VOC increase of 59 mV contributes to active area efficiencies of 14.2% for rear passivated devices with 0.75 µm thick absorber layers, the highest reported value for submicron‐based solution processed, low bandgap CISSe solar cells.

Regulating Hetero-Nucleation Enabling Over 14% Efficient Kesterite Solar Cells.

Developing well-crystallized light-absorbing layers remains a formidable challenge in the progression of kesterite Cu2ZnSn(S,Se)4 (CZTSSe) solar cells. A critical aspect of optimizing CZTSSe lies in accurately governing the high-temperature selenization reaction. This process is intricate and demanding, with underlying mechanisms requiring further comprehension. This study introduces a precursor microstructure-guided hetero-nucleation regulation strategy for high-quality CZTSSe absorbers and well-performing solar cells. The alcoholysis of 2-methoxyethanol (MOE) and the generation of high gas-producing micelles by adding hydrogen chloride (HCl) as a proton additive into the precursor solution are successfully suppressed. This tailored modification of solution components reduces the emission of volatiles during baking, yielding a compact and dense precursor microstructure. The reduced-roughness surface nurtures the formation of larger CZTSSe nuclei, accelerating the ensuing Ostwald ripening process. Ultimately, CZTSSe absorbers with enhanced crystallinity and diminished defects are fabricated, attaining an impressive 14.01% active-area power conversion efficiency. The findings elucidate the influence of precursor microstructure on the selenization reaction process, paving a route for fabricating high-quality kesterite CZTSSe films and high-efficiency solar cells.

Heterojunction reconstruction via In doping towards high-efficiency CZTSSe solar cells

The Cu2ZnSn(S,Se)4 solar cells (CZTSSe) are emerging as a hot area of low-cost thin film photovoltaic technology owing to its non-toxicity and excellent photoelectric properties. However, the large open-circuit voltage deficit (Voc,deficit) caused by the inherently defective CdS/ CZTSSe heterojunction interface is still a huge challenge for improving power conversion efficiency. Herein, we reconstruct the heterojunction interface by inserting a CZTSSe:In into the CdS/CZTSSe heterojunction through an In2Se3 post-deposition treatment. The local occupation of In3+ at Zn2+ and Sn4+ sites decreases the disordered Zn- and Sn-related deep defects and generates benign InZn donors within CZITSSe transition layer simultaneously, which effectively enhances the surface p-to-n conversion. The combination of chemical and field-effect passivation regulates the charge extraction and passivates the charge recombination. As a result, the In element-buried absorber enables the Voc boost from 488 to 527 mV with an impressive active-area efficiency of 13.59 %. These results demonstrate the great potential of the In element-buried absorber in alleviating the Voc,deficit and enhancing the performance of CZTSSe solar cells.

Solvent racing crystallization: Low-solvation dispersion cosolvents for high-quality halide perovskites in photovoltaics

•Designing dispersion cosolvents with reduced solvation capacity •Utilizing solvent polarity and hydrogen-bonding property to their advantage •Promoting the growth of perovskite films with preferred orientation •Attaining solar module (18 cm2 active area) with an efficiency exceeding 22% The solvation capacity of dispersion solvents plays a crucial role in the solution processing of metal halide perovskites. For instance, N,N-dimethylformamide (DMF), a widely used dispersion solvent, possesses high solvation capacity but often generates suboptimal film quality due to slow crystallization kinetics. We propose using low-solvation binary cosolvents (nitrile- and ether-type solvents) to achieve a balance between solvation (i.e., sufficient solubility of precursors) and desolvation (i.e., rapid crystallization of films) processes during perovskite synthesis. The polarity and hydrogen-bonding property of these cosolvents synergistically enhance their solvation capacity, facilitating perovskite precursor dissolution. Moreover, the low-solvation cosolvents accelerate the crystallization of well-defined intermediate films, yielding higher-quality perovskites than those synthesized with DMF. The optimized modules achieved an active-area efficiency of 22.27%, with a certified aperture-area efficiency of 16.10% and corresponding active-area efficiency of 20.75%. This research on solvation regulation provides universal guidelines for innovatively preparing high-quality halide perovskites. The solvation capacity of dispersion solvents plays a crucial role in the solution processing of metal halide perovskites. For instance, N,N-dimethylformamide (DMF), a widely used dispersion solvent, possesses high solvation capacity but often generates suboptimal film quality due to slow crystallization kinetics. We propose using low-solvation binary cosolvents (nitrile- and ether-type solvents) to achieve a balance between solvation (i.e., sufficient solubility of precursors) and desolvation (i.e., rapid crystallization of films) processes during perovskite synthesis. The polarity and hydrogen-bonding property of these cosolvents synergistically enhance their solvation capacity, facilitating perovskite precursor dissolution. Moreover, the low-solvation cosolvents accelerate the crystallization of well-defined intermediate films, yielding higher-quality perovskites than those synthesized with DMF. The optimized modules achieved an active-area efficiency of 22.27%, with a certified aperture-area efficiency of 16.10% and corresponding active-area efficiency of 20.75%. This research on solvation regulation provides universal guidelines for innovatively preparing high-quality halide perovskites.

Bismuth nanoparticles decorated vertically arranged graphene as flexible electrodes for highly efficient detection of Pb(II) ions in water

Plasma enhanced chemical vapor deposition(PECVD) system was used to prepare a vertically arranged graphene (VG) thin-film materials. Bismuth nanoparticles (BiNPs) of different sizes were loaded on VG films by physical vapor deposition (PVD) technique to obtain a BiNPs decorated VG screen-printed electrodes (BiNPs/VG-SPEs) with high sensitivity. The morphology and electrochemical properties of VG-SPE and three BiNPs/VG-SPEs with different sizes of BiNPs were studied by various interface characterization and electrochemical measurements. Compared with pristine VG-SPEs, BiNPs/VG-SPEs demonstrated better electrochemical performance. The electrode with smaller size of BiNPs has the larger electrochemical active area and higher electron transfer efficiency, achieving better electrochemical response to Pb(II) ions. Therefore, VG-SPE with smallest size of BiNPs (4.6 ± 0.5 nm) was utilized to detect Pb(II) ions in aqueous solution. Under the optimized conditions, BiNPs/VG-SPE showed a broader linear concentration range (5–200 μg/L) with a low detection limit (0.15 μg/L). This sensor was also successfully applied for detection of Pb(II) ions in groundwater and tap water. Recovery rates ranged from 96.2 to107.2 % with a relative standard deviation (RSD) less than 6.8 %. It also has good anti-interference and repeatability. Our results provide a promising sensor technique for efficient and rapid in situ monitoring of Pb(II) ions in aquatic environments.

Boost the Efficiency of Cu2ZnSn(S,Se)4 Solar Cell by Using Mn2+‐Induced Ultrathin CdS Buffer Layer

In this article, the efficiency of CZTSSe solar cell is improved by adding manganese chloride in the deposition solution of the CdS buffer layer. The mechanisms behind the experimental results are investigated. On one hand, the MnCl2 can facilitate the deposition of an ultrathin (≈10 nm) CdS buffer layer. The decreased thickness of the buffer layer can reduce the parasitic absorption loss of the solar cell. As the result, the short‐circuit current density of the solar cell is increased. On the other hand, the Mn2+ in the deposition solution can diffuse into the CZTSSe layer during the deposition of the buffer layer. The incorporation of Mn in CZTSSe would decrease the acceptor level of CZTSSe, reduce the defects at the CZTSSe/CdS interface, and increase the activation energy for the main recombination path in CZTSSe solar cell. These can lead to the reduction of the carrier recombination in the depletion region of the solar cell. As the result, the open‐circuit voltage of CZTSSe solar cell is improved. By using the ultrathin CdS buffer layers, the efficiency of CZTSSe solar cell is improved from 10.0% to 12.0% (active area efficiency).

Above 10% efficient electrodeposited Cu2ZnSn(S,Se)4 solar cell achieved by modifying precursor

Electrodeposition is a promising method to fabricate Cu2ZnSn(S,Se)4 (i.e., CZTSSe) absorber layer thanks to its many advantages such as low-cost and large-scale. However, the secondary phases and intrinsic defects in electrodeposited CZTSSe solar cells inevitably limit the photoelectric performance. Herein, two different kind of precursor films (binary-ternary selenide vs. quaternary selenide) are deliberately fabricated and the effect of these precursors on the secondary phases and intrinsic defects of CZTSSe absorber layer are investigated comprehensively. The absorber layer obtained from binary-ternary selenide precursor has a small amount of ZnSe secondary phases and CuSn deep defects, whereas that obtained from the quaternary selenide precursor exhibits the favorable VCu shallow defects, which is beneficial to the efficiency improvement in CZTSSe. Based on the quaternary selenide precursor film, the CZTSSe solar cell with 10.03% total area efficiency (the active area efficiency is 10.9%) was obtained. This is the highest efficiency of CZTSSe solar cells prepared by the electrodeposition method.

Positive Role of Inhibiting CZTSSe Decomposition on Intrinsic Defects and Interface Recombination of 12.03% Efficient Kesterite Solar Cells

Cu2ZnSn(S,Se)4 (CZTSSe) solar cells, which are emerging as promising photovoltaic devices, are currently suffering serious issues of large open‐circuit voltage deficit and low fill factor. Decomposition of CZTSSe is one of many factors limiting the efficiency improvement of CZTSSe solar cells, which can lead to the deviation of the chemical environment during the synthesis of CZTSSe. Herein, the Sn‐vapor is provided during the synthesis of CZTSSe to inhibit the decomposition, and the effect of decomposition on the intrinsic defects and interface recombination are systematically investigated. The high‐quality CZTSSe without the secondary phase and with the low ZnSn and CuZn acceptor defects density is obtained. By inhibiting the decomposition, the recombination activation energy at depletion region is improved and the interface defect density is dramatically decreased, indicating the interface recombination is effectively reduced. Consequently, the performance of CZTSSe thin film solar cells, especially the open‐circuit voltage and fill factor, has been significantly improved. Finally, based on the excellent CZTSSe film, a photovoltaic device with 12.03% efficiency (active area efficiency is 12.96%) is prepared. These encouraging results provide a new route to controlling the defects and interface recombination of CZTSSe solar cells.

Synergic use of two-dimensional materials to tailor interfaces in large area perovskite modules

In the field of halide perovskite solar cells (PSCs), interface engineering has been conceptualized and exploited as a powerful mean to improve solar cell performance, stability, and scalability. In this regard, here we propose the use of a multi two-dimensional (2D) materials as intra and inter layers in a mesoscopic PSCs. By combining graphene into both compact and mesoporous TiO2, Ti3C2Tx MXenes into the perovskite absorbing layer and functionalized-MoS2 at the interface between perovskite and the hole transporting layer, we boost the efficiency of PSCs (i.e., +10%) compared to the 2D materials-free PSCs. The optimized 2D materials-based structure has been successfully extended from lab-scale cell dimensions to large area module on 121 cm2 substrates (11 ×11 cm2) till to 210 cm2 substrates (14.5 ×14.5 cm2) with active area efficiency of 17.2% and 14.7%, respectively. The remarkable results are supported by a systematic statistical analysis, testifying the effectiveness of 2D materials interface engineering also on large area devices, extending the 2D materials-perovskite photovoltaic technology to the industrial exploitation.

Monocrystalline 1.7-eV MgCdTe solar cells

Monocrystalline 1.7 eV Mg0.13Cd0.87Te/MgxCd1−xTe (x > 0.13) double heterostructure (DH) solar cells with varying Mg compositions in the barrier layers are grown by molecular beam epitaxy. A Mg0.13Cd0.87Te/Mg0.37Cd0.63Te DH solar cell featuring abrupt interfaces between barriers and absorber and the addition of a SiO2 anti-reflective coating demonstrate open-circuit voltage (VOC), short-circuit current density (JSC), fill factor (FF), and device active-area efficiencies up to 1.129 V, 17.3 mA/cm2, 77.7%, and 15.2%, respectively. The VOC and FF vary oppositely with the MgxCd1−xTe barrier height, indicating an optimal design of the MgCdTe DHs as a trade-off between carrier confinement and carrier transport. Temperature-dependent VOC measurements reveal that the majority of carrier recombination in the devices occurs outside the DHs, in the a-Si:H hole-contact layer, and at the interface between the a-Si:H layer and the MgxCd1−xTe top barrier at room temperature. Simulation results for the device with the highest efficiency show that the p-type a-Si:H layer and the Mg0.37Cd0.63Te top barrier contribute 1.3 and 2.4 mA/cm2 JSC loss, respectively.

Heterojunction post-heat treatment process driving high efficiency for Cu2ZnSnS4 solar cell

The quality of Cu2ZnSnS4 (CZTS) absorber layer, Mo/CZTS interface and heterojunction CZTS/CdS are the most important factors directly affecting the performance of CZTS solar cells. On the base of high quality absorber layer and back contact interface, the effects of post-heat treatment (PHT) process of CZTS/CdS on the quality of heterojunction and device performance have been comprehensively investigated. The PHT process can promote the elements in the heterojunction region interdiffuse between absorber and buffer layer, i.e., more Cd elements diffuse to CZTS, and Zn, Cu elements diffuse to CdS. Consequently, the elements interdiffusion affects the chemical composition of the absorber layer surface and the band alignment of the heterojunction. After applying the PHT process, the surface of CZTS becomes Cu-poorer in comparison to the CZTS bulk. Due to the diffusion of Cd2+into the CZTS layer, the free carrier density is increased. In addition, PHT process can also promote the recrystallization of CdS and thus greatly improve the crystallization quality of CdS. Owing to the more favorable band alignment at the CZTS/CdS interface as well as better crystallinity of CdS, higher quality heterojunction was obtained. Finally, at the optimized PHT temperature of 275 °C, a pure CZTS solar cell with active area efficiency of 9.75% (total area efficiency: 8.90%) has been fabricated. Based on the application of PHT process, reducing the deep level defects in CZTS bulk is expected to further improve the device performance.

Realization of 11.5% Efficiency Cu2ZnSn(S,Se)4 Thin‐Film Solar Cells by Manipulating the Phase Structure of Precursor Films

Cu2ZnSn(S,Se)4 has been widely regarded as a promising thin‐film solar cell material. In recent years, the development of Cu2ZnSn(S,Se)4 solar cells has encountered a bottleneck, and the higher open‐circuit voltage deficit mainly caused by the secondary phase, CZTSSe/CdS interface recombination, deep‐level defects, and band‐tailing effects has been an outstanding issue. Herein, the influence of the composition and phase distribution of the precursor thin film on the defect and performance of Cu2ZnSn(S,Se)4 solar cells is studied. By modifying the distribution of composition and phase for precursor films, a Cu2ZnSn(S,Se)4 absorber layer without secondary phase and with fewer detrimental defects can be obtained from the pure‐phase precursor film. Thanks to the reduction of the band‐tailing effects, the increase in the depletion width for heterojunction, and the decrease in CZTSSe/CdS interface recombination, the photovoltaic performance of CZTSSe thin‐film solar cells is significantly improved. Finally, based on the excellent kesterite absorber layer, a Cu2ZnSn(S,Se)4 solar cell with 11.51% power conversion efficiency (the active area efficiency is 12.4%) is prepared.

Up-Scalable Fabrication of SnO2 with Multifunctional Interface for High Performance Perovskite Solar Modules

HighlightsHigh-quality large-area SnO2 films are fabricated by chemical bath deposition with the addition of KMnO4.The presence of K and Mn ions can improve both the crystallinity and the phase stability of perovskites and reduce hysteresis of devices simultaneously.Perovskite solar modules (22.4 and 91.8 cm2) are demonstrated with active area efficiencies of 17.26% and 13.72%, respectively, and the 22.4 cm2 perovskite solar module exhibits a T80 operation lifetime exceeding 1000 h in ambient condition.

Biochar induced improvement in root system architecture enhances nutrient assimilation by cotton plant seedlings

BackgroundRaising nitrogen use efficiency of crops by improving root system architecture is highly essential not only to reduce costs of agricultural production but also to mitigate climate change. The physiological mechanisms of how biochar affects nitrogen assimilation by crop seedlings have not been well elucidated.ResultsHere, we report changes in root system architecture, activities of the key enzymes involved in nitrogen assimilation, and cytokinin (CTK) at the seedling stage of cotton with reduced urea usage and biochar application at different soil layers (0–10 cm and 10–20 cm). Active root absorption area, fresh weight, and nitrogen agronomic efficiency increased significantly when urea usage was reduced by 25% and biochar was applied in the surface soil layer. Glutamine oxoglutarate amino transferase (GOGAT) activity was closely related to the application depth of urea/biochar, and it increased when urea/biochar was applied in the 0–10 cm layer. Glutamic-pyruvic transaminase activity (GPT) increased significantly as well. Nitrate reductase (NR) activity was stimulated by CTK in the very fine roots but inhibited in the fine roots. In addition, AMT1;1, gdh3, and gdh2 were significantly up-regulated in the very fine roots when urea usage was reduced by 25% and biochar was applied.ConclusionNitrogen assimilation efficiency was significantly affected when urea usage was reduced by 25% and biochar was applied in the surface soil layer at the seedling stage of cotton. The co-expression of gdh3 and gdh2 in the fine roots increased nitrogen agronomic efficiency. The synergistic expression of the ammonium transporter gene and gdh3 suggests that biochar may be beneficial to amino acid metabolism.

Defect compensation in formamidinium–caesium perovskites for highly efficient solar mini-modules with improved photostability

Formamidinium–caesium mixed-cation perovskites have shown better thermal stability than their methylammonium-containing counterparts but they suffer from photoinstability induced by iodide migration and phase segregation. Here we improve their photostability by adding slightly excessive AX (at a molar percentage of 0.25% to Pb2+ ions), where A is formamidinium or caesium and X is iodine. The excessive AX does not improve the initial solar cell efficiency. It compensates iodide vacancies and suppresses ion migration and defects generation during long-term illumination by around tenfold compared with AX-deficient devices. Consequently, generation of hole traps and phase segregation is impeded, with the former limiting solar cell efficiency after degradation. The perovskite mini-modules reached a certified stabilized efficiency of 18.6% with an aperture area of ~30 cm2, corresponding to an active area efficiency of 20.2%. The mini-module maintains 93.6% of the initial efficiency after continuous operation under 1 sun illumination for >1,000 h at 50 ± 5 °C in air. Methylammonium-free perovskite solar cells have achieved promising efficiency and thermal stability yet iodide migration limits their operational stability. Deng and colleagues show that an excess of formamidinium or caesium iodide precursor suppresses iodide vacancies preventing ion migration and eventually the generation of hole traps during device operation.