Materials Science
Dopant-additive synergism enhances perovskite solar modules
Authors: Bin Ding, Yong Ding, Jun Peng, Jan Romano-deGea, Lindsey E. K. Frederiksen, Hiroyuki Kanda, et al.
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Abstract:
Perovskite solar cells (PSCs) are among the most promising photovoltaic technologies owing to their exceptional optoelectronic properties. However, the lower efficiency, poor stability, and reproducibility issues of large-area PSCs compared with laboratory-scale PSCs are notable drawbacks that hinder their commercialization.
Here we report a synergistic dopant-additive combination strategy using methylammonium chloride (MACl) as the dopant and a Lewis-basic ionic-liquid additive, 1,3-bis(cyanomethyl)imidazolium chloride ([Bcmim]Cl). This strategy effectively inhibits the degradation of the perovskite precursor solution (PPS), suppresses the aggregation of MACl, and results in phase-homogeneous and stable perovskite films with high crystallinity and fewer defects.
This approach enabled the fabrication of perovskite solar modules (PSMs) that achieved a certified efficiency of 23.30% and ultimately stabilized at 22.97% over a 27.22-cm2 aperture area, marking the highest certified PSM performance. Furthermore, the PSMs showed long-term operational stability, maintaining 94.66% of the initial efficiency after 1,000 h under continuous one-sun illumination at room temperature.
The interaction between [Bcmim]Cl and MACl was extensively studied to unravel the mechanism leading to an enhancement of device properties. Our approach holds substantial promise for bridging the benchtop-to-rooftop gap and advancing the production and commercialization of large-area perovskite photovoltaics. Triple-junction solar cells with cyanate in ultrawide-bandgap perovskites
Authors: Shunchang Liu, Yue Lu, Cao Yu, Jia Li, Ran Luo, Renjun Guo, et al.
Link: https://www.nature.com/articles/s41586-024-07226-1
Abstract:
Perovskite bandgap tuning without quality loss makes perovskites unique among solar absorbers, offering promising avenues for tandem solar cells. However, minimizing the voltage loss when their bandgap is increased to above 1.90 eV for triple-junction tandem use is challenging. Here we present a previously unknown pseudohalide, cyanate (OCN−), with a comparable effective ionic radius (1.97Å) to bromide (1.95Å) as a bromide substitute. Electron microscopy and X-ray scattering confirm OCN incorporation into the perovskite lattice. This contributes to notable lattice distortion, ranging from 90.5° to 96.6°, a uniform iodide–bromide distribution and consistent microstrain. Owing to these effects, OCN-based perovskite exhibits enhanced defect formation energy and substantially decreased non-radiative recombination. We achieved an inverted perovskite (1.93 eV) single-junction device with an open-circuit voltage (VOC) of 1.422 V, a VOC× FF (fill factor) product exceeding 80% of the Shockley–Queisser limit and stable performance under maximum power point tracking, culminating in a 27.62% efficiency (27.10% certified efficiency) perovskite–perovskite–silicon triple-junction solar cell with 1 cm2 aperture area. Transition metal tellurides (TMTs) have long been considered ideal candidates for exploring unique properties in fields like condensed-matter physics, chemistry, and materials science. However, despite successful production of TMT nanosheets through top-down exfoliation, their scale has been limited to below the gram level and requires significant processing time, hindering their practical applications.
In this study, a rapid and scalable method for synthesizing various MTe2 (M = Nb, Mo, W, Ta, Ti) nanosheets has been developed. This involves solid lithiation of bulk MTe2 within 10 minutes followed by hydrolysis within seconds. Using NbTe2 as a representative example, over 100 grams (108 g) of NbTe2 nanosheets were produced, with an average thickness of 3.2 nm and average lateral size of 6.2 μm, achieving a high yield (>80%).
Furthermore, intriguing quantum phenomena, such as quantum oscillations and giant magnetoresistance, typically observed only in highly crystalline MTe2 nanosheets, were also observed. These TMT nanosheets demonstrate promising performance as electrocatalysts for lithium-oxygen batteries and electrodes for microsupercapacitors (MSCs). Additionally, this synthesis method proves to be effective for preparing alloyed telluride, selenide, and sulfide nanosheets.
Overall, this work represents a significant advancement in the universal and scalable synthesis of TMT nanosheets, paving the way for exploring new quantum phenomena, potential applications, and commercialization opportunities. Force-controlled release of small molecules offers significant potential for drug delivery and the release of therapeutic or diagnostic agents in medical or materials applications. In the field of polymer mechanochemistry, polymers serve as actuators to stretch mechanosensitive molecules, known as mechanophores. This approach allows for the release of molecular cargo either through rearrangement due to bond scission in a mechanophore, dissociation of cage, supramolecular, or metal complexes, or through 'flex activation'. However, existing systems have been limited in the diversity and quantity of molecules released per stretching event, largely due to challenges in iteratively activating scissile mechanophores, as actuating polymers tend to dissociate after the initial activation. While physical encapsulation strategies can accommodate larger cargo loads, they often suffer from non-specific (i.e., non-mechanical) release.
In this study, researchers demonstrate the efficacy of a rotaxane—a molecule interlocked with a macrocycle trapped on a stoppered axle—as an efficient actuator for triggering the release of cargo molecules attached to its axle. Both in solution, via ultrasonication, and in bulk, through compression, each rotaxane actuator was capable of releasing up to five cargo molecules, achieving release efficiencies of up to 71% and 30%, respectively. This positions the rotaxane device as one of the most efficient release systems developed thus far.
Furthermore, the study showcases the release of three representative functional molecules—a drug, a fluorescent tag, and an organocatalyst—with the anticipation that a wide range of cargo molecules could be released using this device. Thus, the rotaxane actuator presents a versatile platform for various force-controlled release applications. Couple-close construction of polycyclic rings from diradicals
Authors: Alice Long, Christian J. Oswood, Christopher B. Kelly, Marian C. Bryan & David W. C. MacMillan
Link: https://www.nature.com/articles/s41586-024-07181-x
Abstract:
Heteroarenes are prevalent structural motifs in bioactive molecules, possessing favorable physical properties compared to their arene counterparts. Specifically, semisaturated heteroarenes exhibit attractive solubility and a higher fraction of sp3 carbons, thereby enhancing binding affinity and specificity.
However, due to limitations in current synthetic methodologies, these desirable structures are rare. Semisaturated heterocyclic compounds are predominantly synthesized through non-modular, purpose-specific routes, resulting in decreased productivity, limited chemical diversity, and exclusion from many hit-to-lead campaigns.
Here, we present a more intuitive and modular couple-close approach for constructing semisaturated ring systems from dual radical precursors. This strategy combines metallaphotoredox C(sp2)–C(sp3) cross-coupling with intramolecular Minisci-type radical cyclization, enabling the fusion of abundant heteroaryl halides with simple bifunctional feedstocks. These feedstocks serve as diradical building blocks, facilitating the rapid assembly of various spirocyclic, bridged, and substituted saturated ring structures that are challenging to access using conventional methods. The wide availability of required starting materials allows for exploration of underexplored chemical space. Reagent-controlled radical generation ensures highly regioselective and stereospecific annulation, suitable for late-stage functionalization of pharmaceutical scaffolds, thereby replacing lengthy de novo syntheses. Earth Science: One Earth
A global timekeeping problem postponed by global warming
Author: Duncan Carr Agnew
Link:
Abstract:
The historical connection between time and Earth's rotation means that Coordinated Universal Time (UTC) closely tracks this rotation. Because the rotation rate fluctuates, UTC includes discontinuities (leap seconds), complicating its use in computer networks. Since 1972, every UTC discontinuity has necessitated the addition of a leap second.
Research using satellite gravity measurements demonstrates that accelerated melting of the Greenland and Antarctic ice sheets has caused Earth's rotational angular velocity to decrease more rapidly than previously. Adjusting for this effect reveals that since 1972, the angular velocity of Earth's liquid core has been steadily declining at a consistent rate, while the angular velocity of the rest of Earth has been steadily increasing.
Extrapolating these trends to predict future Earth orientation indicates that, by current definitions, UTC will require a negative leap second by 2029. This poses an unprecedented challenge for computer network timing and may necessitate adjustments to UTC sooner than planned. Had polar ice melting not accelerated recently, this issue would arise 3 years earlier: global warming is already impacting global timekeeping.
