Reduced Recombination and Improved Performance of CdSe/CdTe Solar Cells due to Cu Migration Induced by Light Soaking.

The performance of CdTe solar cells has advanced impressively in recent years with the incorporation of Se. Instabilities associated with light soaking and copper reorganization have been extensively examined for the previous generation of CdS/CdTe solar cells, but instabilities in Cu-doped Se-alloyed CdTe devices remain relatively unexplored. In this work, we fabricated a range of CdSe/CdTe solar cells by sputtering CdSe layers with thicknesses of 100, 120, 150, 180, and 200 nm on transparent oxide-coated glass and then depositing CdTe by close-spaced sublimation. After CdCl2 annealing, Cu-doping, and back metal deposition, a variety of analyses were performed both before and after light soaking to understand the changes in device performance. The device efficiency was degraded with light soaking in most cases, but devices fabricated with a CdSe layer thickness of 120 nm showed reasonably good efficiency initially (13.5%) and a dramatic improvement with light soaking (16.5%). The efficiency improvement is examined within the context of Cu ion reorganization that is well known for CdS/CdTe devices. Low-temperature photoluminescence data and Voc versus temperature measurements indicate a reduction in nonradiative recombination due to the passivation of defects and defect complexes in the graded CdSexTe1-x layer.

Evaluation of Resting Tongue Position in Recently Extracted and Long Term Completely Edentulous Patients: A Prospective Interventional Study.

INTRODUCTION: Presence of abnormal resting tongue position can lead to poor denture retention and stability. The prevalence of retracted tongue position has been found to be higher in partially edentulous subjects compared to dentate subjects and is greatest in completely edentulous individuals. AIM: To evaluate resting tongue position in recently extracted and long term completely edentulous patients, and to evaluate the efficacy of achieving retracted tongue position by simple modification in complete denture along with certain tongue exercises. MATERIALS AND METHODS: A total of 62 study subjects were classified into two groups based on duration of edentulousness. Group A: Recently extracted completely edentulous subjects (<1 year), Group B: Long term completely edentulous subjects (>1-10 year). The patients with retracted tongue position were subjected to a simple modification in complete denture along with inclusion of certain tongue exercises. After eight months patients were recalled and evaluated. The data was analysed using SPSS statistical tests like mean, standard deviation, proportion, Chi square test and McNemar Test. RESULTS: Among the study subjects, 54.9% had retracted tongue position. Group B showed high proportion of retracted tongue position (68.8%) as compared to Group A. After the intervention, 42.8% study subjects gained normal resting tongue position. CONCLUSION: Long term completely edentulous subjects presented retracted tongue position in higher percentage when compared to the recently extracted group. The interventional method employed for the subjects with retracted tongue position, played a significant role to assume normal resting tongue position and showed improvement in denture stability and retention.

Evaluation of effectiveness of microwave irradiation for disinfection of silicone elastomeric impression material.

Use of domestic microwave oven has been suggested as a method of disinfecting a number of dental materials used in dental practice. This study was done to analyse the effect of microwave irradiation on vinyl polysiloxane putty impression material (3M ESPE, Express™ STD) contaminated with test organisms (Staphylococcus aureus, Pseudomonas aeruginosa, Candida albicans. 180 square shaped specimens of addition silicon putty material were prepared and divided into 3 groups for three test organisms. The 3 groups were subdivided into 4 subgroups (n = 15) for different exposure parameters (control group 5, 6 and 7 min exposure at 650 W. The specimens were contaminated using standard inoculums of test organism and then were irradiated using domestic microwaves. Broth cultures of the control and test group specimens were plated on selective media culture plates. Colonies formed were counted. Data analyses included Kruskal-Walli's ANOVA and Mann-Whitney's tests. Nil values shows complete elimination of C. albicans and P. aeruginosa after 5, 6 and 7 min exposure. Staphylococcus aureus showed colonies with the mean value of 7.6 × 10(3) ± 2.3 × 10(3), 4.6 × 10(3) ± 2.6 × 10(3) after 5 and 6 min respectively and nil values after 7 min exposure. 5 min exposure caused complete elimination of C. albicans and P. aeruginosa strains, while 7 min exposure eliminated S. aureus completely.

Modification of optical and electrical properties of zinc oxide-coated porous silicon nanostructures induced by swift heavy ion.

Morphological and optical characteristics of radio frequency-sputtered zinc aluminum oxide over porous silicon (PS) substrates were studied before and after irradiating composite films with 130 MeV of nickel ions at different fluences varying from 1 × 1012 to 3 × 1013 ions/cm2. The effect of irradiation on the composite structure was investigated by scanning electron microscopy, X-ray diffraction (XRD), photoluminescence (PL), and cathodoluminescence spectroscopy. Current-voltage characteristics of ZnO-PS heterojunctions were also measured. As compared to the granular crystallites of zinc oxide layer, Al-doped zinc oxide (ZnO) layer showed a flaky structure. The PL spectrum of the pristine composite structure consists of the emission from the ZnO layer as well as the near-infrared emission from the PS substrate. Due to an increase in the number of deep-level defects, possibly oxygen vacancies after swift ion irradiation, PS-Al-doped ZnO nanocomposites formed with high-porosity PS are shown to demonstrate a broadening in the PL emission band, leading to the white light emission. The broadening effect is found to increase with an increase in the ion fluence and porosity. XRD study revealed the relative resistance of the film against the irradiation, i.e., the irradiation of the structure failed to completely amorphize the structure, suggesting its possible application in optoelectronics and sensing applications under harsh radiation conditions.

A comparative study of inter-abutment distance of dies made from full arch dual-arch impression trays with those made from full arch stock trays: an in vitro study.

OBJECTIVES: The dual-arch impression technique is convenient in that it makes the required maxillary and mandibular impressions, as well as the inter-occlusal record in one procedure. The accuracy of inter-abutment distance in dies fabricated from dual-arch impression technique remains in question because there is little information available in the literature. MATERIALS AND METHODS: This study was conducted to evaluate the accuracy of inter-abutment distance in dies obtained from full arch dual-arch trays with those obtained from full arch stock metal trays. RESULTS AND CONCLUSION: The metal dual-arch trays showed better accuracy followed by the plastic dual-arch and stock dentulous trays, respectively, though statistically insignificant. The pouring sequence did not have any effect on the inter-abutment distance statistically, though pouring the non-working side of the dual-arch impression first showed better accuracy.