Conformal GaP layers on Si wire arrays for solar energy applications

We report conformal, epitaxial growth of GaP layers on arrays of Si microwires. Silicon wires grown using chlorosilane chemical vapor deposition were coated with GaP grown by metal-organic chemical vapor deposition. The crystalline quality of conformal, epitaxial GaP/Si wire arrays was assessed by transmission electron microscopy and x-ray diffraction. Hall measurements and photoluminescence show p- and n-type doping with high electron mobility and bright optical emission. GaP pn homojunction diodes on planar reference samples show photovoltaic response with an open circuit voltage of 660 mV

Composition dependent electrochemical properties of earth-abundant ternary nitride anodes

Growing energy storage demands on lithium-ion batteries necessitate exploration of new electrochemical materials as next-generation battery electrode materials. In this work, we investigate the previously unexplored electrochemical properties of earth-abundant and tunable Zn1-xSn1+xN2 (x = -0.4 to x = 0.4) thin films, which show high electrical conductivity and high gravimetric capacity for Li insertion. Enhanced cycling performance is achieved compared to previously published end-members Zn3N2 and Sn3N4, showing decreased irreversible loss and increased total capacity and cycle stability. The average reversible capacity observed is > 1050 mAh/g for all compositions and 1220 mAh/g for Zn-poor (x = 0.2) films. Extremely Zn-rich films (x = -0.4) show improved adhesion; however, Zn-rich films undergo a phase transformation on the first cycle. Zn-poor and stoichiometric films do not exhibit significant phase transformations which often plague nitride materials and show no required overpotential at the 0.5 V plateau. Cation composition x is explored as a mechanism for tuning relevant mechanical and electrochemical properties, such as capacity, overpotential, phase transformation, electrical conductivity, and adhesion. The lithiation/delithiation experiments confirm the reversible electrochemical reactions. Without any binding additives, the as-deposited electrodes delaminate resulting in fast capacity degradation. We demonstrate the mechanical nature of this degradation through decreased electrode thinning, resulting in cells with improved cycling stability due to increased mechanical stability. Combining composition and electrochemical analysis, this work demonstrates for the first time composition dependent electrochemical properties for the ternary Zn1-xSn1+xN2 and proposes earth-abundant ternary nitride anodes for increased reversible capacity and cycling stability

Engineering the reciprocal space for ultrathin GaAs solar cells

III-V solar cells dominate the high efficiency charts, but with significantly higher cost than other solar cells. Ultrathin III-V solar cells can exhibit lower production costs and immunity to short carrier diffusion lengths caused by radiation damage, dislocations, or native defects. Nevertheless, solving the incomplete optical absorption of sub-micron layers presents a challenge for light-trapping structures. Simple photonic crystals have high diffractive efficiencies, which are excellent for narrow-band applications. Random structures a broadband response instead but suffer from low diffraction efficiencies. Quasirandom (hyperuniform) structures lie in between providing high diffractive efficiency over a target wavelength range, broader than simple photonic crystals, but narrower than a random structure. In this work, we present a design method to evolve a simple photonic crystal into a quasirandom structure by modifying the spatial-Fourier space in a controlled manner. We apply these structures to an ultrathin GaAs solar cell of only 100 nm. We predict a photocurrent for the tested quasirandom structure of 25.3 mA/cm$^2$, while a planar structure would be limited to 16.1 mA/cm$^2$. The modified spatial-Fourier space in the quasirandom structure increases the amount of resonances, with a progression from discrete number of peaks to a continuum in the absorption. The enhancement in photocurrent is stable under angle variations because of this continuum. We also explore the robustness against changes in the real-space distribution of the quasirandom structures using different numerical seeds, simulating variations in a self-assembly method

Prospective, non-randomized, parallel group, comparative observational study to compare maternal and neonatal outcome after regional and general anesthesia for Lower Segment Caesarean Section

Background: LSCS is a routine obstetric procedure performed under general anesthesia (GA) or regional anesthesia (RA). Choice of anesthesia depends on factors like gestational age, parity, co-morbidities, urgency of situation, etc. Both GA and RA involve the use of various medications which may influence maternal and neonatal outcome. As there are few studies comparing maternal and fetal outcome in RA and GA for LSCS in Indian population, the present study was taken up. Objectives of the study was to compare the maternal and neonatal outcome after RA and GA for LSCS.Methods: 60 subjects with indications for LSCS were assigned non-randomly into two groups, 30 for GA and 30 for RA, at the discretion of anesthesiologist. The demographic, anthropometric and clinical data was recorded for all subjects. The maternal outcome after RA and GA for LSCS was assessed by parameters like maternal blood loss, postoperative pain, postoperative nausea and vomiting, maternal satisfaction and neonatal outcome by parameters like birth weight, APGAR scores and NICU admissions. The maternal and neonatal outcome between the two groups was compared.Results: All subjects had clear indications for CS. In most of the subjects it was undertaken as an emergency procedure. GA was preferred in high risk subjects. Maternal blood loss, postoperative pain, NICU admissions, need for resuscitation was less under RA compared to GA. There was no difference in PONV, maternal satisfaction, birth weight and need for intubation.Conclusions: LSCS under RA showed a more favourable maternal and neonatal outcome

Study of rationality and utilization pattern of antimicrobials in ear, nose, throat outpatient department of Tertiary Care Hospital, Nanded

Background: Antimicrobials are most commonly prescribed drugs worldwide. Around 50% of the prescriptions of antimicrobial drugs are either not needed, inappropriate or in wrong doses. With the widespread use of antimicrobial agents (AMAs), the prevalence of resistance has increased. To evaluate the prescription pattern and utilization of AMA in ear, nose, throat (ENT) outpatient department (OPD) of Tertiary Care Hospital, Nanded.Methods: This prospective study was conducted in ENT OPD of Dr. Shankarrao Chavan Government Medical College, Nanded over a period of 3 months. During this period, approximately 1100 patients visited ENT OPD and 600 prescriptions were evaluated. The excluded patients were of post-operative follow-up and of patients undergoing medical examination for fitness and handicap certificate. Data were collected by using specially designed case report form. Appropriateness of AMA was assessed by Kunin’s modified criteria.Results: Total 600 prescriptions were analyzed out of which (91%) consist of AMA. Most of them reported with upper respiratory tract infections (URTI) (30.4%), chronic suppurative otitis media (21.4%), acute suppurative otitis media (10.4%), tonsillitis (3.3%), sinusitis (2.7%), and others (15%). Amoxicillin (43.9%) was preferred AMA followed by ciprofloxacin (30.6%), cotrimoxazole (5.8%), azithromycin (3.2%), doxycycline (3.2%) cefixime + clavulanate (3.2%), and amoxicillin + clavulanate (1.8%). Single antibiotic was preferred in all prescriptions. In the concomitant medications, antihistaminics were prescribed in 97.22% of patients, non-steroidal anti-inflammatory drugs in 94.96% of patients, and antacids in 87.76% of patients. Fixed-dose combinations were used in 10% of prescriptions. Brand names of AMA were used in 10% of prescriptions. As per the Kunin’s modified criteria, 83% of patients received AMA therapy appropriately, while 17% patients inappropriately.Conclusions: Amoxicillin is the most common AMA prescribed and URTI is the most common diagnosis made. All AMAs should be prescribed only when needed and should be used in proper dose and for proper duration. Institution wise antibiotic policy should be used to contain resistance. Proper training and regular orientation programs of the juniors’ doctors for judicial use of AMAs will foster the habit of rational prescribing of AMA

GaP/Si wire array solar cells

Si wire arrays have recently demonstrated their potential as photovoltaic devices [1-3]. Using these arrays as a base, we consider a next generation, multijunction wire array architecture consisting of Si wire arrays with a conformal GaN_xP_(1-x-y)As_y coating. Optical absorption and device physics simulations provide insight into the design of such devices. In particular, the simulations show that much of the solar spectrum can be absorbed as the angle of illumination is varied and that an appropriate choice of coating thickness and composition will lead to current matching conditions and hence provide a realistic path to high efficiencies. We have previously demonstrated high fidelity, high aspect ratio Si wire arrays grown by vapor-liquid-solid techniques, and we have now successfully grown conformal GaP coatings on these wires as a precursor to considering quaternary compound growth. Structural, optical, and electrical characterization of these GaP/Si wire array heterostructures, including x-ray diffraction, Hall measurements, and optical absorption of polymer-embedded wire arrays using an integrating sphere were performed. The GaP epilayers have high structural and electrical quality and the ability to absorb a significant amount of the solar spectrum, making them promising for future multijunction wire array solar cells

Characterization of multiterminal tandem photovoltaic devices and their subcell coupling

Three-terminal (3T) and four-terminal (4T) tandem photovoltaic (PV) devices using various materials have been increasingly reported in the literature, but measurement standards are lacking. Here, multiterminal devices measured as functions of two load variables are characterized unambiguously as functions of three device voltages or currents on hexagonal plots. We demonstrate these measurement techniques using two GaInP/GaAs tandem solar cells, with a middle contact between the two subcells, as example 3T devices with both series-connected and reverse-connected subcells. Coupling mechanisms between the subcells are quantified within the context of a simple equivalent optoelectronic circuit. Electrical and optical coupling mechanisms are most clearly revealed using coupled dark measurements. These measurements are sensitive enough to observe very small luminescent coupling from the bottom subcell to the top subcell in the prototype 3T device. Quick simplified measurement techniques are also discussed within the context of the complete characterization