Investigation of Sub-Bandgap Emission and Unexpected n-Type Behavior in Undoped Polycrystalline CdSexTe1-x.

Se alloying has enabled significantly higher carrier lifetimes and photocurrents in CdTe solar cells, but these benefits can be highly dependent on CdSexTe1-x processing. This work evaluates the optoelectronic, chemical, and electronic properties of thick (3 µm) undoped CdSexTe1-x of uniform composition and varied processing conditions (CdSexTe1-x evaporation rate, CdCl2 anneal, Se content) chosen to reflect various standard device processing conditions. Sub-bandgap defect emission is observed, which increased as Se content increased and with "GrV-optimized CdCl2" (i.e., CdCl2 anneal conditions used for group-V-doped devices). Low carrier lifetime is found for GrV-optimized CdCl2, slow CdSexTe1-x deposition, and low-Se films. Interestingly, all films (including CdTe control) exhibited n-type behavior, where electron density increased with Se up to an estimated ≈1017 cm-3. This behavior appears to originate during the CdCl2 anneal, possibly from Se diffusion leading to anion vacancy (e.g., VSe, VTe) and ClTe generation.

Stereocontrolled total synthesis of Resolvin D4 and 17(R)-Resolvin D4.

The total synthesis of Resolvin D4 and its 17(R)-hydroxy-epimer is reported. These lipid-based natural products are biosynthesized from docosahexaenoic acid (DHA, C22:6) during the body's rapid cellular and chemical response to injurious stimuli and are part of a large class of bioactive molecules that resolve inflammation. Our convergent synthesis employed a chiral pool strategy starting from glycidol derivatives and D-erythrose to introduce stereogenic centers. A copper(I)-mediated cross coupling between propargyl bromide and terminal acetylenic precursors yielded core structures of late-stage key intermediates. A simultaneous Lindlar reduction of the skipped diynyl moiety followed by silyl group cleavage securely completed the synthesis. The synthetic availability of these molecules helped further elucidate their stereoselective biofunctions.

Thermomechanical Lift-Off and Recontacting of CdTe Solar Cells.

Controlled delamination of thin-film photovoltaics (PV) post-growth can reveal interfaces that are critical to device performance yet are poorly understood because of their inaccessibility within the device stack. In this work, we demonstrate a technique to lift off thin-film solar cells from their glass substrates in a clean, reproducible manner by first laminating a polymeric backsheet to the device and then thermally shocking the system at low temperatures ( T ≤ -30 °C). To enable clean delamination of diverse thin-film architectures, a theoretical framework is developed and key process control parameters are identified. Focusing on cadmium telluride (CdTe) devices, we show that the lamination temperature and device architecture control the quality of lift-off, while the rate at which the film stack is removed is controlled by the delamination temperature. Crack-free CdTe devices are removed and successfully recontacted, recovering up to 80% of the original device efficiency. The areal density of these devices is ∼0.4 kg m-2, a reduction of over an order of magnitude relative to their initial weight on glass. The framework developed here provides a pathway toward both the development of inexpensive, flexible PV with high specific power and the study of previously buried interfaces in thin-film architectures.

Molecular characterization of the boron adducts of the proteasome inhibitor bortezomib with epigallocatechin-3-gallate and related polyphenols.

The green tea polyphenol epigallocatechin-3-gallate (EGCG) was reported to effectively antagonize the ability of Bortezomib (BZM) to induce apoptosis in cancer cells. This interaction was attributed to the formation of a covalent adduct between a phenolic moiety of EGCG with the boronic acid group of Bortezomib. However, the structural details of this boron adduct and the molecular factors that contribute to its formation and its ability to inhibit Bortezomib's activity remain unclear. This paper describes the use of NMR spectroscopy and cell assays to characterize the structures and properties of the boron adducts of EGCG and related polyphenols. The observed boron adducts included both boronate and borate derivatives, and their structural characteristics were correlated with cell-based evaluation of the ability of EGCG and other phenols to antagonize the anticancer activity of Bortezomib. The enhanced stability of the BZM/EGCG adduct was attributed to electronic and steric reasons, and a newly identified intramolecular interaction of the boron atom of BZM with the adjacent amide bond. The reported approach provides a useful method for determining the potential ability of polyphenols to form undesired adducts with boron-based drugs and interfere with their actions.