Poly(amidoamine) Dendrimer as an Interfacial Dipole Modification in Crystalline Silicon Solar Cells.

Poly(amidoamine) (PAMAM) dendrimers are used to modify the interface of metal-semiconductor junctions. The large number of protonated amines contributes to the formation of a dipole layer, which finally serves to form electron-selective contacts in silicon heterojunction solar cells. By modification of the work function of the contacts, the addition of the PAMAM dendrimer interlayer quenches Fermi level pinning, thus creating an ohmic contact between the metal and the semiconductor. This is supported by the observation of a low contact resistivity of 4.5 mΩ cm2, the shift in work function, and the n-type behavior of PAMAM dendrimer films on the surface of crystalline silicon. A silicon heterojunction solar cell containing the PAMAM dendrimer interlayer is presented, which achieved a power conversion efficiency of 14.5%, an increase of 8.3% over the reference device without the dipole interlayer.

Polymeric Interlayer in CdS-Free Electron-Selective Contact for Sb2Se3 Thin-Film Solar Cells.

High open-circuit voltage in Sb2Se3 thin-film solar cells is a key challenge in the development of earth-abundant photovoltaic devices. CdS selective layers have been used as the standard electron contact in this technology. Long-term scalability issues due to cadmium toxicity and environmental impact are of great concern. In this study, we propose a ZnO-based buffer layer with a polymer-film-modified top interface to replace CdS in Sb2Se3 photovoltaic devices. The branched polyethylenimine layer at the ZnO and transparent electrode interface enhanced the performance of Sb2Se3 solar cells. An important increase in open-circuit voltage from 243 mV to 344 mV and a maximum efficiency of 2.4% was achieved. This study attempts to establish a relation between the use of conjugated polyelectrolyte thin films in chalcogenide photovoltaics and the resulting device improvements.

Influence of Co-Sputtered Ag:Al Ultra-Thin Layers in Transparent V2O5/Ag:Al/AZO Hole-Selective Electrodes for Silicon Solar Cells.

As optoelectronic devices continue to improve, control over film thickness has become crucial, especially in applications that require ultra-thin films. A variety of undesired effects may arise depending on the specific growth mechanism of each material, for instance a percolation threshold thickness is present in Volmer-Webber growth of materials such as silver. In this paper, we explore the introduction of aluminum in silver films as a mechanism to grow ultrathin metallic films of high transparency and low sheet resistance, suitable for many optoelectronic applications. Furthermore, we implemented such ultra-thin metallic films in Dielectric/Metal/Dielectric (DMD) structures based on Aluminum-doped Zinc Oxide (AZO) as the dielectric with an ultra-thin silver aluminum (Ag:Al) metallic interlayer. The multilayer structures were deposited by magnetron sputtering, which offers an industrial advantage and superior reliability over thermally evaporated DMDs. Finally, we tested the optimized DMD structures as a front contact for n-type silicon solar cells by introducing a hole-selective vanadium pentoxide (V2O5) dielectric layer.

25-hydroxyvitamin D levels and hypertension rates.

Vitamin D deficiency has been linked to cardiovascular disease and risk factors including hypertension. The authors sought to determine prevalence rates of hypertension in adults tested for 25-hydroxyvitamin D categorized by their levels and evaluate odds ratios for hypertension at lower 25-hydroxyvitamin D levels compared with optimal levels. A cross-sectional study was conducted January 1, 2004, through December 31, 2006, of patients aged 18 years and older within a large ethnically diverse population. Diagnosis of hypertension was determined by International Statistical Classification of Diseases and Related Health Problems codes. Patients were categorized into quartiles according to 25-hydroxyvitamin D levels: ideal (≥40 ng/mL), adequate (30-39 ng/mL), deficient (15-29 ng/mL), and severely deficient (<15 ng/mL). Prevalence rates of hypertension and odds ratios were calculated for each 25-hydroxyvitamin D quartile, adjusting for age, sex, race, and renal insufficiency. A total of 2722 individuals met the inclusion criteria for the study. The overall prevalence of hypertension in the study population was 24%. Hypertension rates were 52%, 41%, 27%, and 20% in 25-hydroxyvitamin D quartiles <15 ng/mL, 15 to 29 ng/mL, 30 to 39 ng/mL, and ≥40 ng/mL, respectively (P<.001). Odds ratios (95% confidence intervals) for hypertension adjusting for age, sex, race, and renal insufficiency were 2.7 (1.4-5.2), 2.0 (1.5-2.6), and 1.3 (1.2-1.6) for 25-hydroxyvitamin D levels <15 ng/mL, 15 to 29 ng/mL, and 30 to 39 ng/mL, respectively, compared with the ≥40 ng/mL group. This study demonstrates increased rates of hypertension in individuals who tested for lower levels of 25-hydroxyvitamin D starting at levels <40 ng/mL. This retrospective analysis raises the question of whether supplementing to optimal vitamin D levels can prevent or improve hypertension.

Indinavir-induced nephrolithiasis three and one-half years after cessation of indinavir therapy.

Nephrolithiasis is a known side effect of indinavir sulfate, a protease inhibitor used in the treatment of human immunodeficiency virus (HIV). The duration of its side effects, however, has not been well defined. We present a case where a patient presented with symptomatic indinavir-induced nephrolithiasis 3.5 years after discontinuing indinavir. We use this case to illustrate the pathophysiology of indinavir stones and hypothesize how they can occur years after discontinuation by discussing the pharmacokinetics of the drug.