Long-term device stability is the most pressing issue that impedes perovskite solar cell commercialization, given the achieved 22.7% efficiency. The perovskite absorber material itself has been heavily scrutinized for being prone to degradation by water, oxygen and ultraviolet light. To date, most reports characterize device stability in the absence of these extrinsic factors. Here we show that, even under the combined stresses of light (including ultraviolet light), oxygen and moisture, perovskite solar cells can retain 94% of peak efficiency despite 1,000 hours of continuous unencapsulated operation in ambient air conditions (relative humidity of 10–20%). Each interface and contact layer throughout the device stack plays an important role in the overall stability which, when appropriately modified, yields devices in which both the initial rapid decay (often termed burn-in) and the gradual slower decay are suppressed. This extensively modified device architecture and the understanding developed will lead towards durable long-term device performance.

Tailored interfaces of unencapsulated perovskite solar cells for >1,000 hour operational stability

The high natural abundance of silicon, together with its excellent reliability and good efficiency in solar cells, suggest its continued use in production of solar energy, on massive scales, for the foreseeable future. Although organics, nanocrystals, nanowires and other new materials hold significant promise, many opportunities continue to exist for research into unconventional means of exploiting silicon in advanced photovoltaic systems. Here, we describe modules that use large-scale arrays of silicon solar microcells created from bulk wafers and integrated in diverse spatial layouts on foreign substrates by transfer printing. The resulting devices can offer useful features, including high degrees of mechanical flexibility, user-definable transparency and ultrathin-form-factor microconcentrator designs. Detailed studies of the processes for creating and manipulating such microcells, together with theoretical and experimental investigations of the electrical, mechanical and optical characteristics of several types of module that incorporate them, illuminate the key aspects.

Ultrathin silicon solar microcells for semitransparent, mechanically flexible and microconcentrator module designs

Life is mostly composed of the elements carbon, hydrogen, nitrogen, oxygen, sulfur, and phosphorus Although these six elements make up nucleic acids, proteins, and lipids and thus the bulk of living matter, it is theoretically possible that some other elements in the periodic table could serve the same functions Here, we describe a bacterium, strain GFAJ-1 of the Halomonadaceae, isolated from Mono Lake, California, that is able to substitute arsenic for phosphorus to sustain its growth Our data show evidence for arsenate in macromolecules that normally contain phosphate, most notably nucleic acids and proteins Exchange of one of the major bio-elements may have profound evolutionary and geochemical importance

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A Bacterium That Can Grow by Using Arsenic Instead of Phosphorus

Imaging mass spectrometry combines the power of mass spectrometry to identify complex molecules based on mass with sample imaging. Recent advances in secondary ion mass spectrometry have improved sensitivity and spatial resolution, so that these methods have the potential to bridge between high-resolution structures obtained by X-ray crystallography and cyro-electron microscopy and ultrastructure visualized by conventional light microscopy. Following background information on the method and instrumentation, we address the key issue of sample preparation. Because mass spectrometry is performed in high vacuum, it is essential to preserve the lateral organization of the sample while removing bulk water, and this has been a major barrier for applications to biological systems. Recent applications of imaging mass spectrometry to cell biology, microbial communities, and biosynthetic pathways are summarized briefly, and studies of biological membrane organization are described in greater depth.

Advances in Imaging Secondary Ion Mass Spectrometry for Biological Samples

The diffusion behavior at the Cu(In, Ga)Se2 (CIGS)/CdS interface of high efficiency CIGS thin film solar cells has been investigated using energy dispersive x-ray spectroscopy (EDX) and transmission electron microscopy. CdS layers were deposited on CIGS thin films using the chemical bath deposition (CBD) process. EDX analysis revealed that Cd was present in the CIGS layer approximately 100 A from the interface boundary. In contrast to the diffusion of Cd, the Cu concentration decreased near the surface of the CIGS film, suggesting substitution of Cd for Cu atoms. These results are direct evidence of Cd diffusion into CIGS thin films during the CBD process.

Direct evidence of Cd diffusion into Cu(In, Ga)Se2 thin films during chemical-bath deposition process of CdS films

ANALYSIS CONDITIONS. Primary Beam. Primary Beam Energy. Angle of Incidence. Sputtering Rate. Detected Area. Species Monitored. End Point. Energy Distribution. PROFILE ISSUES. Ion Beam Mixing and Depth Resolution. Segregation and Charge Driven Diffusion. Matrix Effects. Surface Effects. Particulates. Crate Shape. Microtopography. Memory Effect. Count Rate Saturation. Sample Location and Mounting. Mass Interferences. QUANTIFICATION. Procedure. Calibration Using Ion Implantation. Systematic Trends in RSFs. SPECIFIC APPLICATIONS. Bulk Analysis. Metals and Rough Surfaces. Insulators. Interfaces. Multilayers. Residual Gas Elements. Small Areas. Major Elements. Appendices. Index.

Robert G. Wilson

Papers

Secondary Ion Mass Spectrometry: A Practical Handbook for Depth Profiling and Bulk Impurity Analysis