Structural and chemical characterization of the back contact region in high efficiency CdTe solar cells

Cadmium telluride (CdTe) is the leading commercialized thin-film photovoltaic technology. Copper is commonly used in back contacts to obtain high efficiency, but has also been implicated as a harmful factor for device stability. T hus it is critical to understand its composition and distribution within complete devices. In this work the composition and structure of the back contact region was examined in high efficiency devices (-16%) contacted using a ZnTe:Cu buffer layer followed by gold metallization. T he microstructure was examined in the asdeposited state and after rapid thermal processing (RTP) using high resolution transmission electron microscopy and EDX chemical mapping. After RTP the ZnTe exhibits a bilayer structure with polycrystalline, twinned grains adjacent to Au and an amorphous region adjacent to CdTe characterized by extensive Cd-Zn interdiffusion. T he copper that is co-deposited uniformly within ZnTe is found to segregate dramatically after RTP activation, either collecting near the ZnTe/Au interface or forming CUxTe clusters in CdTe at defects or grain boundaries near the interface with ZnTe. Chlorine, present throughout CdTe and concentrated at grain boundaries, does not penetrate significantly into the back contact region during RTP activation

Congenital Hypogonadotropic Hypogonadism Due to GNRH Receptor Mutations in Three Brothers Reveal Sites Affecting Conformation and Coupling

Congenital hypogonadotropic hypogonadism (CHH) is characterized by low gonadotropins and failure to progress normally through puberty. Mutations in the gene encoding the GnRH receptor (GNRHR1) result in CHH when present as compound heterozygous or homozygous inactivating mutations. This study identifies and characterizes the properties of two novel GNRHR1 mutations in a family in which three brothers display normosmic CHH while their sister was unaffected. Molecular analysis in the proband and the affected brothers revealed two novel non-synonymous missense GNRHR1 mutations, present in a compound heterozygous state, whereas their unaffected parents possessed only one inactivating mutation, demonstrating the autosomal recessive transmission in this kindred and excluding X-linked inheritance equivocally suggested by the initial pedigree analysis. The first mutation at c.845 C>G introduces an Arg substitution for the conserved Pro 282 in transmembrane domain (TMD) 6. The Pro282Arg mutant is unable to bind radiolabeled GnRH analogue. As this conserved residue is important in receptor conformation, it is likely that the mutation perturbs the binding pocket and affects trafficking to the cell surface. The second mutation at c.968 A>G introduces a Cys substitution for Tyr 323 in the functionally crucial N/DPxxY motif in TMD 7. The Tyr323Cys mutant has an increased GnRH binding affinity but reduced receptor expression at the plasma membrane and impaired G protein-coupling. Inositol phosphate accumulation assays demonstrated absent and impaired Gαq/11 signal transduction by Pro282Arg and Tyr323Cys mutants, respectively. Pretreatment with the membrane permeant GnRHR antagonist NBI-42902, which rescues cell surface expression of many GNRHR1 mutants, significantly increased the levels of radioligand binding and intracellular signaling of the Tyr323Cys mutant but not Pro282Arg. Immunocytochemistry confirmed that both mutants are present on the cell membrane albeit at low levels. Together these molecular deficiencies of the two novel GNRHR1 mutations lead to the CHH phenotype when present as a compound heterozygote

0801 Sleep, Nightmares, and the Maintenance of Posttrauma Symptoms

Abstract Introduction Most individuals will experience at least one traumatic event in their lifetime. Although most individuals who experience a trauma will exhibit some posttrauma symptoms, only a small subset will experience long-lasting symptoms. In fact, most research suggests that posttrauma symptoms will gradually reduce over time. However, some individuals can exhibit posttrauma symptoms for an extended period of time. Although research has demonstrated that poor overall sleep quality may explain why some people have trouble gradually recovering from posttrauma symptoms, research has yet to examine specific aspects of sleep that can impair the gradual remission of posttrauma symptoms. This study examined how individual facets of sleep quality (such as nightmares and sleep duration) impact posttrauma symptoms over time. Methods 944 college students completed an online survey battery that included measures of traumatic experiences, time since trauma (TST), posttrauma symptoms, sleep quality, and the presence of nightmares. Regression analyses were used to examine the interaction of sleep quality sub-facets and time since trauma on posttrauma nightmares (PNMs). Results Out of 944 participants, 637 (67%) reported at least one trauma. Of those students, time since trauma (TST) and all other sleep variables significantly predicted posttrauma symptoms (p &amp;lt; 0.05). However, the only significant interaction was nightmares and TST (p &amp;lt; 0.01) where individuals who experienced PNMs had significantly (p &amp;lt; 0.01) higher posttrauma symptom intercept (48.19) than individuals who did not experience PNMs (31.19). Furthermore, individuals who experienced PNMs demonstrated statistically significant flatter slopes than those without nightmares (p &amp;lt; 0.01). Conclusion The results reveal that time since trauma predicts a decrease in posttrauma symptoms, whereas nightmares impede this symptom reduction. Interestingly, the interaction finding suggests that nightmares play a critical role in initial symptom expression and recovery. These results demonstrate the importance of identifying and treating nightmares immediately following a trauma. Support “none” </jats:sec

Structural and chemical evolution of the CdS:O window layer during individual CdTe solar cell processing steps

© 2017 Elsevier Ltd Oxygenated cadmium sulfide (CdS:O) is often used as the n-type window layer in high-performance CdTe heterojunction solar cells. The as-deposited layer prepared by reactive sputtering is XRD amorphous, with a bulk composition of CdS 0.8 O 1.2 . Recently it was shown that this layer undergoes significant transformation during device fabrication, but the roles of the individual high temperature processing steps was unclear. In this work high resolution transmission electron microscopy coupled to elemental analysis was used to understand the evolution of the heterojunction region through the individual high temperature fabrication steps of CdTe de position, CdCl 2 activation, and back contact activation. It is found that during CdTe deposition by close spaced sublimation at 600 °C the CdS:O film undergoes recrystallization, accompanied by a significant (∼30%) reduction in thickness. It is observed that oxygen segregates during this step, forming a bi-layer morphology consisting of nanocrystalline CdS adjacent to the tin oxide contact and an oxygen-rich layer adjacent to the CdTe absorber. This bilayer structure is then lost during the 400 °C CdCl 2 treatment where the film transforms into a heterogeneous structure with cadmium sulfate clusters distributed randomly throughout the window layer. The thickness of window layer remains essentially unchanged after CdCl 2 treatment, but a ∼25 nm graded interfacial layer between CdTe and the window region is formed. Finally, the rapid thermal processing step used to activate the back contact was found to have a negligible impact on the structure or composition of the heterojunction region