Photons as a 21st century reagent

A pharmaceutical industry viewpoint on how the fundamental laws of photochemistry are used to identify the parameters required to implement photochemistry from lab to scale. Parameters such as photon stoichiometry and light intensity are highlighted within to inform future publications

A detailed study of irradiation requirements towards an efficient photochemical Wohl‐Ziegler procedure in flow

A platform has been developed to enable standardization of light sources, allowing consistent scale‐up from high‐throughput screening in batch to flow, using the same pseudo‐monochromatic light source. The impact of wavelength and light intensity on a photochemical reaction was evaluated within this platform using the Wohl‐Ziegler benzylic bromination of 4‐methyl‐3‐(trifluoromethyl)benzonitrile with N‐bromosuccinimide as a model system. It was found that only 40 % of the maximum light intensity was required while still maintaining reaction rate, allowing more reliable temperature control and lower energy consumption. The optimized reaction conditions were subsequently applied to a range of synthetically relevant (hetero)aromatic compounds under continuous conditions, exploring the scope of the process within a mild and scalable procedure

Accurate band alignment of sputtered Sc₂O₃ on GaN for high electron mobility transistor applications

Abstract Sc2O3 is a promising gate dielectric for surface passivation in GaN-based devices. However, the interface quality and band alignment of sputtered Sc2O3 on GaN has not been fully explored. In this work, x-ray photoelectron spectroscopy (XPS) and variable angle spectroscopic ellipsometry were performed to extract the discontinuities in the valence and conduction bands of the Sc2O3/GaN system. Sc2O3 films were deposited on GaN using radio frequency sputtering. The valence band offset of Sc2O3/GaN was determined to be 0.76 ± 0.1 eV using Kraut’s method. The Sc2O3 band gap of 6.03 ± 0.25 eV was measured using O 1s energy loss spectroscopy. The electron affinity measurements of GaN and Sc2O3 using XPS secondary electron cut-off spectra provided an additional degree of accuracy to the derived band line-up for the Sc2O3/GaN interface. The band alignment results were compared with literature values of band offsets determined experimentally and theoretically for differently grown Sc2O3 films on GaN.</jats:p

Fine-Tuning Heat Stress Algorithms to Optimise Global Predictions of Mass Coral Bleaching

Increasingly intense marine heatwaves threaten the persistence of many marine ecosystems. Heat stress-mediated episodes of mass coral bleaching have led to catastrophic coral mortality globally. Remotely monitoring and forecasting such biotic responses to heat stress is key for effective marine ecosystem management. The Degree Heating Week (DHW) metric, designed to monitor coral bleaching risk, reflects the duration and intensity of heat stress events and is computed by accumulating SST anomalies (HotSpot) relative to a stress threshold over a 12-week moving window. Despite significant improvements in the underlying SST datasets, corresponding revisions of the HotSpot threshold and accumulation window are still lacking. Here, we fine-tune the operational DHW algorithm to optimise coral bleaching predictions using the 5 km satellite-based SSTs (CoralTemp v3.1) and a global coral bleaching dataset (37,871 observations, National Oceanic and Atmospheric Administration). After developing 234 test DHW algorithms with different combinations of the HotSpot threshold and accumulation window, we compared their bleaching prediction ability using spatiotemporal Bayesian hierarchical models and sensitivity–specificity analyses. Peak DHW performance was reached using HotSpot thresholds less than or equal to the maximum of monthly means SST climatology (MMM) and accumulation windows of 4–8 weeks. This new configuration correctly predicted up to an additional 310 bleaching observations globally compared to the operational DHW algorithm, an improved hit rate of 7.9%. Given the detrimental impacts of marine heatwaves across ecosystems, heat stress algorithms could also be fine-tuned for other biological systems, improving scientific accuracy, and enabling ecosystem governance

Defect limitations in Cu2ZnSn(S, Se)(4) solar cells utilizing an In2S3 buffer layer

Alternative n-type buffer layer such as In2S3 has been proposed as a Cd-free alternative in kesterite Cu2ZnSn(S,Se)4 (CZTSSe) solar cells. In this study, optical and electronic characterization techniques together with device analysis and simulation were used to assess nanoparticle-based CZTSSe absorbers and solar cells with CdS and In2S3 buffers. Photoluminescence spectroscopy indicated that CZTSSe absorbers with In2S3 buffer had a lower density of detrimental non-radiative defects and a higher concentration of copper vacancies V+Cu, responsible for p-type conductivity in CZTSSe, in comparison to the absorber with CdS buffer. Capacitance–voltage (C–V) measurements revealed that the In2S3 buffer-based CZTSSe devices had a three times higher apparent doping density and a consequently narrower space charge region than devices with a CdS layer. This resulted in poorer collection of photo-generated charge carriers in the near-IR region despite a more favorable band alignment as determined by x-ray photoelectron and inverse photoelectron spectroscopy. The presence of interfacial defect states in In2S3 devices as determined by C–V and biased quantum efficiency measurements is also responsible for the loss in open-circuit voltage compared with reference devices with CdS

Density Functional Theory and Experimental Determination of Band Gaps and Lattice Parameters in Kesterite Cu2ZnSn(SxSe1-x)4

The structures and band gaps of copper-zinc-tin selenosulfides (CZTSSe) are investigated for a range of anion compositions through experimental analysis and complementary first-principles simulations. The band gap was found to be extremely sensitive to the Sn-anion bond length, with an almost linear correlation with the average Sn-anion bond length in the mixed anion phase Cu2ZnSn(S x Se1-x)4. Therefore, an accurate prediction of band gaps using first-principles methods requires the accurate reproduction of the experimental bond lengths. This is challenging for many widely used approaches that are suitable for large supercells. The HSE06 functional was found to predict the structure and band gap in good agreement with the experiment but is computationally expensive for large supercells. It was shown that a geometry optimization with the MS2 meta-GGA functional followed by a single point calculation of electronic properties using HSE06 is a reasonable compromise for modeling larger supercells that are often unavoidable in the study of point and extended defects