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Potential Induced Degradation(PID) is an important field degradation mode that can cause warranty claims. Quantum Efficiency (QE) of the cells inside modules degraded by PID needs to be known in order to reduce the uncertainty in the flash I-V measurement of modules. QE measurement of a cell in a PID degraded module can also assist in diagnosing the reasons for the degradation. The cell whose QE needs to be measured must be shaded and maintained at short circuit condition. The load point of the module needs to be calculated to ensure this. The challenges in estimating the load point for PID degraded modules are illustrated through the simulation study. The applicability of the method for finding the load point is tested for degraded, partially degraded and non-degraded cells in the PID affected module. It is explained that the method is valid for non-degraded and partially degraded cells. The cells that are degraded don’t give expected short circuit current due to considerable errors. Hence the QE results won’t be accurate for degraded cells in a PID affected module.

Establishing short circuit condition for a cell in a module is an essential prerequisite for measuring the quantum efficiency of a solar cell. A PV module consists of cells in series and also has bypass diodes across strings. To measure the quantum efficiency of a cell (target cell) it is necessary to shade the cell so that it acts as a current limiting cell. In this paper, we use a PSpice model of a PV module. By using current voltage characteristics of the module, we evolve at a methodology to determine the applied bias to bring the target cell to short circuit condition. These simulation results are compared with experimental results obtained on a solar simulator of a 60 cell solar module having bypass diodes.

Degradation in electrical performance of photovoltaic (PV) modules is related to the degradation of the solar cells and laminate materials in the modules, which often shows up as hot spots in infrared (IR) thermography. The analysis of the IR data of crystalline silicon modules inspected in the field during the All India Survey of Photovoltaic Module Reliability in 2016 is being presented in this paper, along with its correlation to the electrical degradation in these modules. The thermal mismatch in the PV modules has been quantified in terms of a Thermal Mismatch Index, based on the difference between the highest cell temperature and the representative module temperature. Modules with high thermal mismatch (hot cells) under MPPT condition show high power degradation, caused mainly due to fill factor degradation. Modules with hot cells show higher degradation in "Hot" climatic zones as compared with " Non-Hot" climates. The analysis indicates that modules having cracks and hot cells have higher power degradation than modules having cracks but no hot cells. This indicates that the worst cracks tend to create hot cells in the modules, while the benign cracks (which have lesser impact on power output) do not affect the cell temperature to that extent.

Catering to a large undergraduate laboratory class requires the experiments to be robust, low maintenance, and easy to set up with low cost test equipment at the disposal of most university laboratories. Most introductory undergraduate semiconductor device laboratory courses utilize packaged semiconductor integrated circuit chips to illustrate the functioning and applications of fundamental semiconductor devices such as diodes and transistors. While such methods do justice to the illustration of device concepts, the packages abstract the device physics and manufacturing and promote a "black-box" mentality towards device engineering. We have proposed and implemented a novel undergraduate device laboratory experiment, where metal oxide semiconductor capacitor (MOSCAP) devices were designed and fabricated at our university cleanroom and provided to students to perform basic capacitance-voltage profile measurements. To allow over a hundred students to simultaneously perform the experiments, we fabricated miniature test jigs that served as probe stations with spring-loaded pogo pins to make electrical contact with the devices. Using a simple op-amp based circuit that is easy for second year undergraduates to analyze, students are able to successfully extract device parameters such as substrate doping density and flat-band voltage using this experiment, and visualize the different modes of operation of a MOSCAP. (C) 2018 American Association of Physics Teachers.

We investigate the role of n-type organic molecule, bathocuproine (BCP), additive in perovskite semiconductor film based solar cells using first principle calculations and optoelectronic studies. A state-of-art high fill factor of 0.82 and improved open circuit voltage of 0.95 V for CH3NH3PbI3 (MAPI) based perovskite solar cells are achieved in addition with highly improved (more than one order) electroluminescence efficiency. Delayed emission spectroscopy does not show any blue shift peak or double peak emission suggests no structural changes in 3D perovskite. Contact angle studies using water droplet supports BCP is forming a capping layer to boost moisture barrier. Our experimental findings regarding no 2D structure formation has also been supported by first-principles electronic structure calculations based on DFT in MAPI after insertion of BCP. Furthermore, calculations suggest that a physisorption type of interaction has been found in between MAPI and BCP with an average distance of 2.9 A. These res...

The photoluminescence (PL) decay of hybrid halide perovskite single crystals (MAPbX(3), MA = CH3NH3+, Pb = Pb2+, X = Br-, and I-) is measured over 4 orders of magnitude in intensity over the time scales of 100s of nanoseconds to a few microseconds. This long PL decay is non-exponential, suggesting the presence of a distribution of carrier relaxation times. Spectro-temporal studies show that the emission peak red-shifts with increasing time. The physics of this problem is closely related to donor-acceptor pair recombination in crystalline semiconductors and recombination in a-Si:H. Based on these models, we present a simple model to account for the recombination dynamics in the perovskite systems. This model also accounts for the fluence dependence of the recombination kinetics. In this model, a fraction of the photogenerated electrons and holes are trapped in localized states. The electrons tunnel to the hole sites for recombination. The broad distribution of lifetimes is a consequence of the fact that the tunneling probability is very sensitive to the separation of electron-hole pairs, and PL decay dynamics is a function of excitation fluence, i.e., carrier density generated by optical excitation. The red-shift arises from the fact that holes and electrons are trapped at different energies.

We present experimental evidence showing that the effective carrier diffusion length ($L_d$) and lifetime ($\tau$) depend on the carrier density in MAPbBr$_3$ single crystals. Independent measurements reveal that both $L_d$ and $\tau$ decrease with an increase in photo-carrier density. Scanning photocurrent microscopy is used to extract the characteristic photocurrent $I_{ph}$ decay-length parameter, $L_d$, which is a measure of effective carrier diffusion. The $L_d$ magnitudes for electrons and holes were determined to be ~ 13.3 $\mu$m and ~ 13.8 $\mu$m respectively. A marginal increase in uniform light bias ($\leq 5 \times 10^{15}$ photons/cm$^2$) increases the modulated photocurrent magnitude and reduces the $L_d$ parameter by a factor of two and three for electrons and holes respectively, indicating that the recombination is not monomolecular. The $L_d$ variations were correlated to the features in photoluminescence lifetime studies. Analysis of lifetime variation shows intensity-dependent monomolecular and bimolecular recombination trends with recombination constants determined to be ~ 9.3 $\times 10^6$ s$^{-1}$ and ~ 1.4 $\times 10^{-9}$ cm$^{3}$s$^{-1}$ respectively. Based on the trends of $L_d$ and lifetime, it is inferred that the sub-band-gap trap recombination influences carrier transport in the low-intensity excitation regime, while bimolecular recombination and transport dominate at high intensity., Comment: 19 pages, 6 figures

Electroluminescence (EL) imaging is an essential tool that signifies the inactive areas (dark area in the image) in a PV module which are not visible to the naked eye. A total of ~700 EL images of fielded PV modules taken during the All India Survey of Photovoltaic Module Reliability 2018 (AIS-2018) were considered for this study. Out of the 700 modules, a majority of modules were from large sites (system size > 100 kW). In the analysis, apart from cell cracks, 14 types of defects/ patterns were observed, out of which seven types were not observed in the earlier 2016 Survey. Cracks are segregated into 3 categories, out of which approximately 80% of the modules showed mode A (hairline) cracks. The correlation analysis of observed cracks with I-V data analysis of the corresponding modules indicates that an increased number of cracks led to increase in fill factor (FF) degradation. Out of 700 modules, 92 modules were inspected in both surveys conducted in 2016 and 2018. Out of these 92 modules, 7 modules shown increase in interconnect failure, and 3 modules show drastic changes in number of cell cracks.

A high efficiency (> $$18\%$$ ) industrial large area crystalline silicon wafer solar cell fabrication process generally requires industrial equipment with large footprint, high capital and running costs. Stricter processing window, continuous monitoring and automated functioning are the reasons for it. However, for any conventional laboratory (lab) it is always difficult to manage these requirements with limited available lab space or insufficient fund and other related resources. In this work, we report a novel way to fabricate high efficiency full area aluminium back surface field monocrystalline silicon wafer solar cells in our lab using low-cost processing with small-footprint fabrication tools for 6 inch pseudo-square industrial wafers. The novelty of our work includes optimization of every fabrication process step, e.g., texturization, emitter diffusion, emitter passivation and anti-reflection coating deposition, edge-isolation, screen printing and co-firing individually. These modifications include tuning of processing tools and processes, utility changes and inclusion of additional process steps. Beaker-based chemical processes, manual diffusion furnace, introduction of low temperature oxidation, low temperature silicon nitride deposition processes, plasma-edge isolation tool, single manual screen printer, single oven drying of metal pastes and co-firing using rapid thermal processing tools were used at our lab. For our cells, actual and active area efficiencies of 18.5 and 19% (measured under AM1.5G 1 Sun condition), respectively, were achieved.

In this work, we report a low-cost, industrially viable chemical oxidation process (named as NCPRE-oxide process) using sodium hypochlorite (NaOCl) solution applicable to 5-inch pseudo-square monocrystalline silicon Al-BSF solar cells. Introduction of this new ultrathin oxide layer in between silicon nitride layer and silicon shows the improvement in the open circuit voltage and thereby the efficiency of solar cells.

Photoluminescence (PL) imaging has emerged as an important tool for obtaining the spatial variation of the electronic and electrical parameters of Si wafer and solar cells. Since this is a contactless measurement, spatial lifetime maps can be obtained at different stages of processing. This paper consists of two parts. In the first part we describe a low cost PL imaging tool developed at NCPRE. Improvements in image quality using both hardware and software approaches will be presented. In the second part, we present various case studies of how processing affects minority carrier lifetime and series resistance.

This paper presents the analysis of the poorperforming PV modules observed in All-India Survey of PV Module Reliability 2016. The analysis shows that cracks in the cells, which lead to fill factor loss are one of the main causes of the high degradation rates. Also, higher encapsulant and metallization discoloration is seen in poorly performing modules. These modules are mostly found in small rooftop systems installed in recent years. The presence of cracks and excessive discoloration indicate that the quality of modules and/or installation procedures is not satisfactory at these sites.

This paper presents the analysis of the electroluminescence (EL) images taken on site during the All India Survey of Photovoltaic Module Reliability 2016. Cracks have been detected in most of the PV modules which show poor performance. The percentage of cracked cells is higher in young (age 5 years) modules, and also in modules rack-mounted on the roof compared to those mounted on the ground. The power degradation rate was found to increase with increase in the number of cracks in the PV module. Cracks were found to cause fill factor degradation in the modules which is responsible for the power degradation.

In many architectural projects, solar panels are integrated to buildings and other structures, with aesthetics given the highest priority. In many such cases the mounting does not provide free flow of air on the backside of module. This paper presents the effects of a metal (aluminum) back plate in various configurations on the temperature and performance of the PV modules. It is found that if a back plate is necessary for mounting the modules, it is beneficial to ensure tight contact of the plate with the backsheet of the module, to avoid any air gap that would retard the heat dissipation and lead to higher module operating temperatures. Having a dark outside surface on the plate further helps to dissipate heat.

In this paper, a unique low-cost, low-temperature chemical passivation process (named as NCPRE-oxide) is investigated. This process uses only a single chemical to grow an ultrathin oxide layer of thickness~ 1.7 nm on the silicon surface. Being a single component chemical process, the solution is homogeneous which helps in uniform growth of silicon oxide layer. Our study establishes that the introduction of this chemical oxide layer in between silicon and silicon nitride improves passivation on both n-type and p-type surfaces. An enhancement in the effective minority carrier lifetime $(\tau_{\text{eff}})$ is also observed on the pyramidal textured surface with chemical oxide/silicon nitride stack for both the p-base and phosphorous diffused silicon surface. The versatility of the NCPRE-oxide is verified by X-ray photoelectron spectroscopy (XPS), carrier lifetime measurements and photoluminescence (PL) imaging.

This paper presents the electrical performance data gathered in the 3r All India Survey of Photovoltaic Module Reliability conducted in 2016, in which a total of 925 modules were inspected in different climatic zones of India. The average degradation rate of the Group A (‘All’ sites) modules is 1.23%/year and the so-called ‘Good’ sites is 0.63%/year, better than that observed in the 2014 Survey, the reason being partly the inclusion of more large PV power plants, and also discounting of 2% LID in 2016 analysis methodology. The modules in ‘Hot’ climates degrade faster than modules in ‘Non-Hot’ climates, consistent with earlier results. Modules in small systems (capacity 100 kW). Roof-mounted systems also degrade at a faster rate than ground-mounted systems.

In this paper, a new method is explored for translating measured I-V characteristics of a module to STC conditions, with emphasis on suitability for PV field survey. The prediction accuracy of our proposed `Standard Irradiance Desired Temperature' (SIDT) method has been compared to a modified IEC 60891 procedure-1 and the Anderson model-based procedure. It has been shown that the proposed SIDT method results in a normalized root mean square error of less than ±1 % in maximum power, whereas the other two methods result in an error of more than ± 2 %. The SIDT method is also shown to be better for predicting other parameters at STC conditions.

Discoloration of encapsulant is one of the primary causes behind the decrease in power output of field aged PV modules. It would be beneficial to develop a method for quantifying the discoloration based on visual photography and establish a correlation with the power degradation. We hereby describe techniques for analyzing visual images to quantify the discoloration, with the ultimate aim of estimating the short circuit current degradation. Our analysis shows that it is possible to estimate the Yellowness Index of discolored areas in PV modules from the visual images, and it correlates well with the reduction in short circuit current density (calculated from quantum efficiency measurements).

This paper presents the analysis of visual degradation data collected during an All-India Survey of Photovoltaic Mod- ule Degradation conducted in 2013, in which 57 crystalline silicon modules were inspected in the five different climatic zones of In- dia. Analysis of the data indicates that the highest percentage of modules suffered discoloration in the Hot and Dry climatic zone, with the Hot and Humid zone coming in second in the list. A higher percentage of modules have suffered corrosion in the Hot and Hu- mid zone, as compared with other zones. The modules installed in the Cold climate suffered the least degradation. Both discoloration and corrosion have been seen in modules across all age groups, even in some of the modules installed less than five years ago. On the other hand, delamination and backsheet degradation have been seen only in modules more than a decade old. The visual degrada- tion data have been correlated with the electrical performance data and reaffirm the direct relation between encapsulant discoloration and reduction in short-circuit current and output power, as well as that of series resistance with metal corrosion.

The All India Survey of Photovoltaic Module Reliability 2014 is an enhanced version of the survey conducted in the previous year, with detailed characterization of PV modules including current-voltage, infrared and electroluminescence imaging, visual inspection, insulation resistance test and interconnect breakage test. More than a thousand modules were inspected in the field and the main results of the survey are presented in this paper. The average Pmax degradation rate for the so-called ‘good’ modules (Group X) is 1.33%/year which is higher than that commonly projected by manufacturers, and widely employed in financial calculations. Modules falling in the ‘not-so-good’ category (Group Y) show even higher degradation rates, and it is at least partly due to higher number of micro-cracks in the modules, and increased degradation of the packaging materials like encapsulant, backsheet, etc. Modules in ‘Hot’ climates degrade faster than modules in the ‘Non-Hot’ climates. Degradation in fill factor is the primary cause for performance degradation in the young modules (ages

This paper reports quantitative correlation of CH3NH3PbBr3 (MAPbBr(3)) thin film morphology to light emitting diode efficiency parameters. Sequential (spin coating) deposition is used for highly reproducible and dense film morphology of MAPbBr(3) thin-film. In this fabrication process using an orthogonal solvent approach, control of morphology, coverage, thickness, and optical properties in these compact thin-films is demonstrated. Optical studies show direct correlation between morphology to dynamics of photoluminescence (PL) and absolute PL yield. Perovskite light emitting diodes (PeLEDs) are fabricated from these films to find the best ratio of PbBr2 versus MABr for optimal performance. This study demonstrates PeLEDs with high brightness, approximate to 1050 cd m(-2) at 4.7 V (luminance efficiency approximate to 0.1 cd A(-1)), for optimal thin-film process with state-of-the-art device performance. This quantitative analysis suggests that these state-of-the-art PeLEDs suffer from poor charge carrier balance (approximate to 2%) and out-coupling efficiency (approximate to 6%). Interestingly, charge carrier balance and PL yield together can explain the change in PeLED efficiency modulation with film morphology. Studies on single carrier devices show that these PeLEDs are electron current dominated and charge carrier balance increases with operating bias voltage.

Photoluminescence imaging under different bias conditions is used to obtain maps of the local series resistance and the local ideality factor in large area industrial silicon solar cells. The variation in series resistance correlates with the variations in emitter sheet resistance.

In this Letter, we investigate the temperature dependence of the optical properties of methylammonium lead iodide (MAPbI(3) = CH3NH3PbI3) from room temperature to 6 K. In both the tetragonal (T > 163 K) and the orthorhombic (T < 163 K) phases of MAPbI3, the band gap (from both absorption and photoluminescence (PL) measurements) decreases with decrease in temperature, in contrast to what is normally seen for many inorganic semiconductors, such as Si, GaAs, GaN, etc. We show that in the perovskites reported here, the temperature coefficient of thermal expansion is large and accounts for the positive temperature coefficient of the band gap. A detailed analysis of the exciton line width allows us to distinguish between static and dynamic disorder. The low-energy tail of the exciton absorption is reminiscent of Urbach absorption. The Urbach energy is a measure of the disorder, which is modeled using thermal and static disorder for both the phases separately. The static disorder component, manifested in the exciton line width at low temperature, is small. Above 60 K, thermal disorder increases the line width. Both these features are a measure of the high crystal quality and low disorder of the perovskite films even though they are produced from solution.

This paper presents an analysis of the electrical and visual degradation data gathered in the 2nd All India Survey of Photovoltaic Module Reliability, conducted in 2014, in which a total of 1148 modules were inspected in different climatic zones of India. The modules in the Hot Climates are seen to degrade faster than modules in the Non-Hot climates. Fill Factor (FF) reduction has been found to be the main cause for power reduction in young modules (less than 5 years old), while for old modules (more than 5 years), I sc reduction is the main culprit. Visual degradation in the modules has been quantified and correlated with the degradation in various electrical parameters. The degradation in I sc correlates with the discoloration and delamination of the encapsulant and the degradation in the FF correlates well with the extent of the corrosion in the metallization.

Photocarrier generation mechanisms in 3,6-diaryl-N-hexylcarbazole (aryl = p-cyanophenyl and p-acetophenyl) were studied in single-layer, bilayer, and blend film devices in sandwich geometry between...

Neural tube closure is a complex spatio-temporal process. Multiple neural tube defects (NTDs) in a single patient are extremely rare. Only a few cases of multiple NTDs have been reported in the world literature, including less than 20 cases of double NTDs and 3 cases of triple NTDs. We report a fourth case of triple NTDs and review the literature regarding the embryogenesis. An effort is made to understand the theories of neural tube closure in light of recent advances in molecular biology and identification of the signaling pathways involved.

In this paper, we report on an integrated OLED― photodetector organic device using 3,6-dipyrenyl-N-hexylcarbazole (P2NHC) as the active layer. This device is an efficient blue emitter in forward bias and an efficient visible-blind UV photodetector in reverse bias. In forward bias, the device (as a blue emitter) has a low turn on voltage (2.7 V), a current efficiency of 2.0 cd/A for a brightness of 200-9000 cd/m 2 , and low droop at higher brightness. In reverse bias, the device has a saturated photoresponse of 77 mA/W at 390 nm, which corresponds to an internal quantum efficiency of 64%. The spectral response of a photodetector-only device indicated that carriers are generated in the interface of P2NHC/cathode. The singlet exciton diffusion length of P2NHC was determined to be 7.8 ± 1 nm, which is too small to account for the high photodetector efficiency. Alternate mechanisms are discussed to account for the high photodetector efficiency.

Synthesis, structure, optical absorption, emission and electroluminescence properties of a new blue emitting Al complex, namely, bis-(2-amino-8-hydroxyquinolinato), acetylacetonato Al(III) are reported. Multilayer OLED using the Al complex showed blue emission at 465 nm, maximum brightness of ∼ 425 cd/m2 and maximum current efficiency of 0.16 cd/A. Another multilayer OLED using the Al complex doped with phosphorescent Ir complex showed ‘white’ light emission, CIE coordinate (0.41, 0.35), maximum brightness of ∼ 970 cd/m2 and maximum current efficiency of 0.53 cd/A.

Objective The use of ventriculo-peritoneal shunts having antisiphon device has been reported in adult patients, but there is a dearth of experience with such shunts in pediatric age group. This study is being undertaken to compare the effectiveness of these types of shunt for the treatment of congenital hydrocephalus. Patients and methods Forty patients with congenital hydrocephalus with or without neural tube were divided randomly into two groups (A and B). Patients in antisiphon group were treated with shunts with differential valve including antisiphon device (Vygon ® shunt) while patients in non-antisiphon group were treated with differential valve shunts (Chhabra shunt and Ceredrain ® ). Mann–Whitney test, asymmetric t -test and Chi-square test were used to assess the correlation and the significance. Results The mean age was 3.5 months and 3.4 months in antisiphon group and non-antisiphon group, respectively. The M:F ratio was 2.3:1 in antisiphon group while it was 3:1 in non-antisiphon group. The mean decrease in OFC was more in non-antisiphon group than antisiphon group during the follow up from 3 months to 6 months while mean decrease in MEI was more in non-antisiphon group from 0 month to 3 months than antisiphon group. There were two cases of shunt overdrainage in non-antisiphon group. The shunt blockage rate was 20% in antisiphon group and 15% in non-antisiphon group, respectively. There was 20% and 15% shunt infection rate in antisiphon group and non-antisiphon group, respectively. This study demonstrated overdrainage syndrome in two of the patients of differential valve shunts. Conclusion Though rare, complication associated with overdrainage is certainly a problem in children. In our study, the patients who received shunts with antisiphon device do not show any overdrainage.

N-N'-diphenyl-N,N'-(bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine) (TPD), was used to fabricate single layer devices (ITO/TPD/Ca/Al). A near-white emission (CIE coordinate of 0.25, 0.24) is observed in electroluminescence (EL) of the single layer device with prominent emission bands at 400, 475 and 670 nm. Steady state and time-resolved emission spectra of spin-coated and annealed TPD films and TRES and TRANES analysis confirmed that emission at 400 and 475 nm are due to monomer and excimer emission, respectively. The origin of the red emission at 670 nm in EL is discussed.

3,6-diarylcarbazole derivatives, 3,6-di-(p-cyanophenyl)-N-hexylcarbazole (CNHC) and 3,6-di-(p-acetylphenyl)-N-hexylcarbazole (ANHC) were synthesized, characterized and energy levels determined. Steady state fluorescence of these molecules showed blue emission in thin films. Blends of these molecules with N,N'-diphenyl-N,N'-(bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine (TPD) showed exciplex emission as the dominant one. Single layer organic light emitting devices (OLEDs) of CNHC, ANHC and their blends with TPD were fabricated using ITO as anode and Ca as cathode. The blend film devices showed pure exciplex electroluminescence.

Purpose To investigate the association of angiotensin-converting enzyme (ACE) gene insertion/deletion (I/D) polymorphism and other risk factors with renal scarring in patients with posterior urethral valves (PUV). Materials and methods Forty consecutive patients from North-west India were treated for PUV in 1997–2004. The patients were divided into group 1 (no renal scarring, n = 12) and group 2 (renal scars present, n = 28) based on dimercato-succinic acid scans. ACE I/D polymorphism was determined by polymerase chain reaction in PUV patients and unrelated healthy controls (n = 100). Results Mean age at presentation was 23.7 ± 37.2 months and mean follow up was 4.8 ± 1.5 years. Preoperative mean serum creatinine levels for group 1 (non-scarred) and group 2 (scarred) were 1.1 ± 1.6 mg/dl and 1.7 ± 1.6 mg/dl, respectively. One year after treatment, the serum creatinine levels had decreased to 0.6 ± 0.1 mg/dl and 0.8 ± 0.3 mg/dl in group 1 and group 2, respectively. ACE genotype distribution in children with PUV was no different from that of controls. The occurrence of D allele was significantly (p = 0.04) higher in patients of group 2. Multivariate logistic regression analysis showed that D allele had a significant impact on renal scar formation, introducing a 4.6-fold risk (odds ratio 4.6, 95% confidence interval 1.03–20.38, p = 0.04). A highly significant correlation between the occurrence of renal scarring and presence of breakthrough urinary tract infection (odds ratio = 7.5, 95% confidence interval 1.60–35.07, p = 0.006) and serum creatinine at follow up (odds ratio = 0.6, 95% confidence interval 0.47–0.81, p = 0.03) was observed. The mean values for glomerular filtration rate (GFR) after 1 year of treatment (p = 0.006) and at follow up (p = 0.027) were significantly different between the patients with II genotype and ID/DD genotype. Hypertension was observed in 13 patients and proteinuria in nine patients with no significant difference between the patients having II/I D/DD genotypes. Conclusion The presence of D allele is associated with progression of renal scarring and reduced GFR in PUV patients.

Charge separation at organic-organic (O-O) interfaces is crucial to how many organic-based optoelectronic devices function. However, the mechanism of formation of spatially separated charge carriers and the role of geminate recombination remain topics of discussion and research. We review critically the contributions of the various factors, including electric fields, long-range order, and excess energy (beyond the minimum needed for photoexcitation), to the probability that photogenerated charge carriers will be separated. Understanding the processes occurring at the O/O interface and their relative importance for effective charge separation is crucial to design efficient solar cells and photodetectors. We stress that electron and hole delocalization after photoinduced charge transfer at the interface is important for efficient free carrier generation. Fewer defects at the interface and long-range order in the materials also improve overall current efficiency in solar cells. In efficient organic cells, external electric fields play only a small role for charge separation.

We report on the structural, morphological and optical properties of AB(Br(1-x)Cl(x))3 (where, A = CH3NH3(+), B = Pb(2+) and x = 0 to 1) perovskite semiconductor and their successful demonstration in green and blue emissive perovskite light emitting diodes at room temperature. The bandgap of perovskite thin film is tuned from 2.42 to 3.16 eV. The onset of optical absorption is dominated by excitonic effects. The coulomb field of the exciton influences the absorption at the band edge. Hence, it is necessary to explicitly account for the enhancement of the absorption through the Sommerfield factor. This enables us to correctly extract the exciton binding energy and the electronic bandgap. We also show that the lattice constant varies linearly with the fractional chlorine content satisfying Vegards law.

The performance of photovoltaic modules depends on temperature and irradiance. It is necessary to translate the measured I–V characteristics to standard test condition for assessing degradation, and such translations require temperature coefficients for voltage and current. Prediction of the annual energy yield also requires knowledge of the temperature coefficients. IEC 60891 provides a standard procedure for measurement of temperature coefficients and this methodology has been utilized to obtain the temperature coefficients of modules of different PV technologies, both in laboratory and in the field. Comparison of the values obtained in the field with those of the laboratory show good conformance. Also the variation of the temperature coefficients with change in irradiance has been investigated.

This paper presents an overview of the 2nd All India Survey of Photovoltaic Module Degradation, conducted in the months of September to December 2014. A total of 1080 modules belonging to different photovoltaic technologies were inspected from 45 different sites which are spread across the 5 different climatic zones of India. This is the first survey in India in which electroluminescence, illuminated and dark I–V measurements, insulation resistance and various other tests were carried out on PV modules installed in the field. The goal of the survey is to determine the degradation in the field-aged PV modules and find correlations between visual, electrical and physical degradation of the PV modules. The purpose of this paper is to present an overview of the survey methodology and statistics to the PV community.

The present work investigates the variation of minority carrier lifetime of silicon wafers after each processing step during the fabrication of silicon solar cells. Contactless photoconductance technique provides quantitative measure of the average lifetime. The spatial variation in the minority carrier lifetime is obtained by photoluminescence imaging. By combining these two techniques, we obtain the following significant results: i) edge isolation process degrades the lifetime near the wafer boundaries, ii) removal of phosphosilicate glass after POCl3 diffusion degrades lifetime in the central region of the wafer, iii) high temperature processing steps e.g. emitter diffusion and contact firing result in improving / recovering the lifetime.

Aim To retrospectively review the occurrence of renal scarring in patients with posterior urethral valves (PUV), and correlate it with various causative factors. Methods The records of 52 patients treated for PUV by the authors were reviewed. Patients with vesico-ureteric reflex (VUR) dysplasia syndrome were excluded from the study. The patients were divided into group I (no renal scarring, n = 18) and group II (renal scars present, n = 34) based on dimercapto-succinic acid scans. The mode of treatment, presence/absence of breakthrough urinary tract infections (UTI), presence/absence of history of nocturnal/diurnal incontinence, presence/absence of VUR, stable postoperative serum creatinine, rate of drainage of ureters on diethylene triamine penta acetic acid (DTPA) scans and management of bladder dysfunction, if any, were noted. The presence or absence of renal scarring was statistically correlated with occurrence of any of the above factors. Results Primary valve fulguration was performed in 41 patients and 11 patients had an initial vesicostomy. The median follow up was 3.5 years (range 1.5–15 years). Renal scarring was present in either kidney in 34 patients (bilateral 14, unilateral 20). The mode of initial treatment did not affect the incidence or rate of scarring. The preoperative and postoperative serum creatinine at the end of 1 year did not differ between the two groups. Presence/severity of VUR did not affect the pattern of renal scarring. A highly significant correlation between the occurrence of renal scarring and presence of diurnal incontinence (P ≤ 0.007, odds ratio = 4.5) and breakthrough UTI (P ≤ 0.002, odds ratio = 7.0) was observed. There was also correlation with slow drainage in the ureters on a DTPA scan (P ≤ 0.0005). Detrusor instability and low compliance on urodynamic assessment did not affect occurrence in the limited number of patients studied. The rate of somatic growth in both groups was retarded as compared to normal healthy counterparts. Conclusion Breakthrough UTI, diurnal incontinence and poor drainage of ureters on DTPA are associated with a higher incidence of renal scarring. Mode of initial treatment, presence or absence of VUR, and bladder abnormalities do not affect renal scarring in the short term.

The synthesis of two tert -amine-based, non-fluorescent, hole-transport molecules (4,4′-[bis-{(4-di- n -hexylamino)benzylideneamino)]stilbene ( DHABS ) and 4,4′-[bis-{(4-diphenylamino)benzylideneamino}]stilbene) ( DPABS ) that are suitable for spin coating on indium tin oxide (ITO) for electronic device fabrication is described and compared with the widely used TPD. Electroluminescence occurred at a turn-on voltage of 7–8 V in ITO/hole-transport layer (HTL, spin coated)/Alq 3 /Al devices.

Some new 5-substituted 8-hydroxyquinoline derivatives and their Al(III) complex dyes (Al(2)3–Al(9)3) have been synthesised. The compounds were characterized by 1H, 13C, mass and elemental analysis. The aluminium complexes retain the spectroscopic properties of the parent compound, namely, tris(8-hydroxyquinolinato) aluminium (III) (AlQ3). In dichloromethane solution, these aluminium complexes show absorption maxima in the range of 390–395 nm, strong green luminescence in the range 527–536 nm and aluminium complexes show high fluorescence quantum yield in solution and thin films. The fluorescence decay in solution as well as in thin film is fitted to biexponential with τav ranging from 3 to 9 ns. Electroluminescence (EL) of the spin-cast film of Al(3)3 (3 = 5-(2-ethylhexyloxymethyl)-8-hydroxyquinoline) as the emitting layer was performed and the turn-on voltage for the EL device is about 11 V.

In this paper, we report on transient electroluminescence (EL) studies in (ITO/TPD/alloy/Alq 3 /Al) organic light emitting diodes. The alloy in the active layer is a co-evaporated mixture of TPD + Alq 3 in the ratio TPD:Alq 3 = 1:4. These results were compared with the transient EL response of a standard device (ITO/TPD/Alq 3 /Al). The EL response of the alloy device consists of two components – a fast component (10–20 μs) and a slow component (200–300 μs). It is shown that the slow component arises due to the leakage of electrons from the Alq 3 layer into the alloy layer and subsequent exciton formation in the alloy layer. The magnitude of the fast component depends on the pulse repetition rate and temperature. This is shown to be related to the presence of deep traps in the alloy layer. The presence of deep traps is also confirmed by current transients in the alloy device.

This paper presents a comparative prospective study of three modalities of surgical treatment for extrahepatic portal hypertension in children: central splenorenal shunt after splenectomy (CSS), side-to-side lienorenal shunt (SSLR) without splenectomy, and splenectomy and gastroesophageal devascularization (SGD). In an 18-month period, 27 procedures were performed: 10 CSS, 10 SSLR, and seven SGD. The outcomes were evaluated by fall in portal pressures, hematological parameters, shunt patency, splenic regression, and disappearance of esophageal varices. All three procedures were comparable in the fall of portal pressure after surgery. The average blood loss and operating time were statistically significant in favor of SSLR compared with CSS. At 3-month follow-up, shunt patency was confirmed by duplex Doppler study in all the patients in the SSLR group and in nine out of 10 patients in the CSS group. In the CSS and SGD groups, hypersplenism resolved in all the patients. In the SSLR group, blood counts improved in only five out of eight affected children. No patient re-bled during a follow-up of 3-5 years. There were no cases of hepatic encephalopathy or overwhelming postsplenectomy sepsis. In conclusion, CSS is useful when there is a large spleen, severe hypersplenism, and a shuntable splenic vein. SSLR is suitable when there is only mild splenomegaly, mild hypersplenism, and a shuntable splenic vein. Splenectomy and devascularization is the choice when there is no shuntable splenic vein.

Transient electroluminescence of an organic alloy-based light-emitting device (ITO/TPD/alloy/Alq/Al) was studied and the results compared with a standard device without the alloy layer. Under forward bias condition, the electroluminesence (EL) of the alloy device consisted of two components, a fast (10–20 μs) and a slow (200–300 μs) component. The slow component in the EL matched with a corresponding matching current transient. These transients are identified with the leakage of electrons into the alloy region across the alloy/Alq interface and subsequent exciton formation in the alloy layer. A large overshoot in EL intensity was also observed in the turn-off transient of the standard and alloy devices. The variations in the EL overshoot and decay at different forward bias voltages, repetition rates and temperatures were used to understand the role of traps in the device structures.

The photoluminescence (PL) spectra and PL decays of poly-p-phenylene vinylene (PPV) film prepared by the solvent-free, room temperature UV polymerization method were studied at 300 and 77 K. The analysis of the emission wavelength dependent luminescence decays of PPV film showed a lifetime distribution that varied in a systematic manner with emission wavelength. The oscillatory variation of PL decay (and average lifetime) with emission wavelength at 77 K is a new result. These results are consistent with the model that the PL of PPV film is due to energetically disordered excitons and thermally activated PL quenching is a dominant mechanism.