Environmental stability of perovskite solar cells (PSCs) has been improved by trial-and-error exploration of thin low-dimensional (LD) perovskite deposited on top of the perovskite absorber, called ...the capping layer. In this study, a machine-learning framework is presented to optimize this layer. We featurize 21 organic halide salts, apply them as capping layers onto methylammonium lead iodide (MAPbI
) films, age them under accelerated conditions, and determine features governing stability using supervised machine learning and Shapley values. We find that organic molecules' low number of hydrogen-bonding donors and small topological polar surface area correlate with increased MAPbI
film stability. The top performing organic halide, phenyltriethylammonium iodide (PTEAI), successfully extends the MAPbI
stability lifetime by 4 ± 2 times over bare MAPbI
and 1.3 ± 0.3 times over state-of-the-art octylammonium bromide (OABr). Through characterization, we find that this capping layer stabilizes the photoactive layer by changing the surface chemistry and suppressing methylammonium loss.
The bandgap of CuIn1-xGaxSe2 (CIGS) chalcopyrite semiconductors can be tuned between ≈1.0 and ≈1.7 eV for Ga contents ranging between x = 0 and x = 1. While an optimum bandgap of 1.34 eV is desirable ...for achieving maximum solar energy conversion in solar cells, state‐of‐the‐art CIGS‐based devices experience a drop in efficiency for Ga contents x > 0.3 (i.e., for bandgaps >1.2 eV), an aspect that is limiting the full potential of these devices. The mechanism underlying the limited performance as a function of CIGS composition has remained elusive: both surface and bulk recombination effects are proposed. Here, the disentanglement between surface and bulk effects in CIGS absorbers as a function of Ga content is achieved by comparing photogenerated charge carrier dynamics in air/CIGS and surface‐passivated ZnO/CdS/CIGS samples. While surface passivation prevents surface recombination of charge carriers for low Ga content (x < 0.3; up to 1.2 eV bandgap), surface recombination dominates for higher‐bandgap materials. The results thus demonstrate that surface, rather than bulk effects, is responsible for the drop in efficiency for Ga contents larger than x ≈ 0.3.
The mechanism responsible for the limited performance of high‐Ga CuIn1‐xGaxSe2 (CIGS) solar cells has remained elusive. Photogenerated charge carrier dynamics are studied as a function of Ga content by means of optical pump–terahertz probe on air/CIGS and ZnO/CdS/CIGS samples, allowing for the disentanglement between surface and bulk recombination processes.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Approximately half of the world's 500,000 new oesophageal squamous-cell carcinoma (ESCC) cases each year occur in China. Here, we show whole-genome sequencing of DNA and RNA in 94 Chinese individuals ...with ESCC. We identify six mutational signatures (E1-E6), and Signature E4 is unique in ESCC linked to alcohol intake and genetic variants in alcohol-metabolizing enzymes. We discover significantly recurrent mutations in 20 protein-coding genes, 4 long non-coding RNAs and 10 untranslational regions. Functional analyses show six genes that have recurrent copy-number variants in three squamous-cell carcinomas (oesophageal, head and neck and lung) significantly promote cancer cell proliferation, migration and invasion. The most frequently affected genes by structural variation are LRP1B and TTC28. The aberrant cell cycle and PI3K-AKT pathways seem critical in ESCC. These results establish a comprehensive genomic landscape of ESCC and provide potential targets for precision treatment and prevention of the cancer.
Breast cancer metastasis remains a clinical challenge, even within a single patient across multiple sites of the disease. Genome-wide comparisons of both the DNA and gene expression of primary tumors ...and metastases in multiple patients could help elucidate the underlying mechanisms that cause breast cancer metastasis. To address this issue, we performed DNA exome and RNA sequencing of matched primary tumors and multiple metastases from 16 patients, totaling 83 distinct specimens. We identified tumor-specific drivers by integrating known protein-protein network information with RNA expression and somatic DNA alterations and found that genetic drivers were predominantly established in the primary tumor and maintained through metastatic spreading. In addition, our analyses revealed that most genetic drivers were DNA copy number changes, the TP53 mutation was a recurrent founding mutation regardless of subtype, and that multiclonal seeding of metastases was frequent and occurred in multiple subtypes. Genetic drivers unique to metastasis were identified as somatic mutations in the estrogen and androgen receptor genes. These results highlight the complexity of metastatic spreading, be it monoclonal or multiclonal, and suggest that most metastatic drivers are established in the primary tumor, despite the substantial heterogeneity seen in the metastases.
•III-V and SiGe alloys can achieve optimum bandgap combinations for MJSC on Si.•State of the art GaAsP/SiGe solar cells on Si substrates uses thick buffer layers.•In this work, GaAsP/SiGe solar cells ...have been made with reverse graded buffer layers.•These tandem GaAsP/SiGe solar cells have been developed on porous Si substrates.•Reverse buffers can be thinner, and Si porous layers mitigate the formation of cracks.•Our porous layer has reduced the crack density but does not totally suppress them.•Functional tandem GaAsP/SiGe solar cells have been demonstrated.
III-V compound semiconductors and SiGe alloys can be combined to develop multijunction solar cells on Silicon substrates with optimum bandgap combinations. Current implementations of such devices have reached efficiencies over 20%, using thick –and thus costly– buffer layers which induce the appearance of cracks in large area samples. As a strategy to mitigate these two issues (thick buffers and cracking), a GaAsP/SiGe tandem solar cell has been developed employing group IV reverse graded buffer layers grown on Ge/Si virtual substrates with a subsurface Silicon porous layer. Reverse buffer layers facilitate a reduction in the threading dislocation density with limited thicknesses but can also induce cracks. To minimise this, a porous silicon layer has been incorporated close to the Ge/Si interface so that the ductility of this layer suppresses crack propagation. In terms of solar cell performance, this porous layer reduces the problem of cracks, not totally supressing them though. Accordingly, the low shunt resistance observed in previous designs has been increased thus improving solar cell efficiency, which is still notably behind designs using thicker forward graded buffer layers. The first results of this new architecture are presented here.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In this work we investigate the effect of rapid thermal annealing (RTA) on the performance of solar cells consisting of different GaAsSbN-based structures and correlate the device results with ...modifications of the optical and structural properties of the alloy. In particular, bulk layers grown at different growth rates and type-II GaAsSb/GaAsN superlattices with different period thickness are analyzed. We find evidences of material quality improvement after the annealing process such as a reduction of N-related radiative defects and Sb clusters. These RTA-induced changes lead to a notable enhancement of the open circuit voltage (VOC), which results in values of the bandgap-voltage offset (WOC = EG/q-VOC) comparable to that of a non-optimized reference GaAs solar cell with the same device structure (WOC ∼0.63 eV). The decrease in WOC after annealing shows a correlation with the reduced radiative recombination at low energy N-related sub-bandgap states. These results suggest that radiative recombination in a broad band of deep defect states is a source of VOC degradation in GaAsSbN solar cells.
•Sub-bandgap deep radiative states induced by N are present in GaAs(Sb)N.•Reduction of the N-related radiative defect density after rapid thermal annealing.•Elimination of sub-bandgap optically active states correlates with enhanced VOC.•WOC values of GaAsSbN solar cells comparable to reference GaAs cell (∼0.63 eV).
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In the search for a hybrid III-V/Si photovoltaic technology, a tandem GaAsP/SiGe solar cell grown on silicon substrate have been developed using SiGe/Ge reverse graded buffers. Reverse buffer layers ...can be made thinner than conventional designs, favour the reduction of the threading dislocation density and allow the growth of thicker active layers in the same growth time, but also facilitate the appearance of cracks. In this work, experimental results of functional tandem solar cell devices manufactured with this approach and strategies for their optimization are presented.
•Reverse graded buffers have been used to implement tandem III-V/SiGe solar cells grown on silicon substrates.•A combined epitaxial process using CVD for the group-IV and MBE for the III-Vs has been used.•A working dual-junction solar cell has been demonstrated as a proof-of-concept.•The solar cell performance is limited by a high density of cracks.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
B-cell receptor (BCR) repertoire profiling is an important tool for understanding the biology of diverse immunologic processes. Current methods for analyzing adaptive immune receptor repertoires ...depend upon PCR amplification of VDJ rearrangements followed by long read amplicon sequencing spanning the VDJ junctions. While this approach has proven to be effective, it is frequently not feasible due to cost or limited sample material. Additionally, there are many existing datasets where short-read RNA sequencing data are available but PCR amplified BCR data are not.
We present here V'DJer, an assembly-based method that reconstructs adaptive immune receptor repertoires from short-read RNA sequencing data. This method captures expressed BCR loci from a standard RNA-seq assay. We applied this method to 473 Melanoma samples from The Cancer Genome Atlas and demonstrate V'DJer's ability to accurately reconstruct BCR repertoires from short read mRNA-seq data.
V'DJer is implemented in C/C ++, freely available for academic use and can be downloaded from Github: https://github.com/mozack/vdjer CONTACT: benjamin_vincent@med.unc.edu or parkerjs@email.unc.eduSupplementary information: Supplementary data are available at Bioinformatics online.
Bandgap engineering and quantum confinement in semiconductor heterostructures provide the means to fine‐tune material response to electromagnetic fields and light in a wide range of the spectrum. ...Nonetheless, forming semiconductor heterostructures on lattice‐mismatched substrates is a challenge for several decades, leading to restrictions for device integration and the lack of efficient devices in important wavelength bands. Here, it is shown that the van der Waals epitaxy of 2D GaSe and InSe heterostructures occur on substrates with substantially different lattice parameters, namely silicon and sapphire. The GaSe/InSe heteroepitaxy is applied in the growth of quantum wells and superlattices presenting photoluminescence and absorption related to interband transitions.
The epitaxy of GaSe/InSe quantum wells and superlattices on c‐sapphire and Si (111) substrates is presented. These van der Waals materials cover a wide range of energies for optoelectronics applications, with few competing materials. The GaSe/InSe Quantum Wells exhibited photoluminescence in confined states and the observed energies agree with the proposed theoretical models.
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