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A study was carried out to analyze the economics of fish production and marketing in Dang district of Nepal. Structured survey was done with 75 respondents (45 producers, 5 wholesalers, 10 retailers, and 15 consumers) in three different sites of Dang district (viz: Lamahi Municipality, Rapti Rural Municipality and Gadhawa Rural Municipality). The initial investment, cost of production and returns, production function, price spread,and marketing margin, and ranking of production and marketing problems of fish were done by index ranking techniques. Financial analysis showed that the total initial investment per hectare of fishpond was found to be NRs. 9, 68,394 with the annual production cost of NRs. 6, 93,483. The total return was found to be NRs. 932,088 and net profit realized per hectare was NRs. 238,604. Out of total cost, about 73.70% was variable cost and the remaining 26.30% was fixed cost. Of the total variable cost, the cost of feed (58.63%) was significantly higher followed by the cost of fingerlings (12.94%), labor (11.37%), manure and fertilizer cost (8.33%) fuel/ energy (4.46%) and maintenance cost (4.27%) respectively. The benefit cost ratio (B/C ratio) was found to be 1.82 which implies that the fish enterprise was found to be profitable in the study area. The research also revealed that the producer’s share was 78.17% with price spread of 71.57 and marketing efficiency of 90.81%. The value sum of the estimated parameters associated with all the inputs is 0.52 which indicates the decreasing return to scale. Lack of technological know-how and unavailability of inputs on time are the major production problems. Inefficient price information system and competition with the Indian fish are the major marketing problems. Thus, for sustainable production and marketing of fish government should focus primarily on technological dissemination and better pricing policy.

Using nationally representative data from 40 low- and middle-income countries, the authors find very low use of important CVD preventive medications, including blood pressure lowering drugs, statins, and aspirin.

The government of Nepal has recommended blanket fertilizer application for rice cultivation, which results in lower nutrient use efficiency (NUE) particularly under rainfed conditions. With the aim of finding an appropriate nutrient management practices concerning rice production and profitability, a field experiment was conducted during rainy season of 2017 and 2018 at Kavrepalanchowk and Dang district of Nepal. Altogether, five treatments comprising various nutrient management practices viz. Nutrient Expert Model (NE), use of Leaf Color Chart (LCC), Government Recommended Fertilizer Dose (GON), Farm Yard Manure (FYM), and Farmers’ Field Practice (FFP), were laid out in RCBD with four replications in farmers’ fields. The analysis of variance showed significant difference between treatments for test weight and grain yield in Kavrepalanchowk whereas all traits except number of effective tillers were significant in Dang. The significantly higher grain yield and harvest index were obtained in NE, followed by LCC; and the overall straw yield was highest in LCC, followed by NE in both the locations. Also, yield gap analysis suggested the NE had 44.44% and 23.97% increase in yield as compared to FPP in Kavrepalanchowk and Dang, respectively. The combined analysis with Best Linear Unbiased Estimator revealed the interaction of nutrient management and location significantly effects the straw yield and harvest index across both the locations. The estimated mean straw yield and harvest index were 10.93 t/ha and 34.98%, respectively. Both correlation study and biplot of principal component analysis signaled grain yield had positive correlation with all other traits. Furthermore, the net revenue was maximum for NE, followed by LCC in both the locations. The benefit: cost ratio was highest for NE which was 1.55 in Kavrepalanchowk and 2.61 in Dang. On the basis of these findings, NE and LCC can be effectively used as nutrient management practice by the farmers to obtain maximum production and profitability in Rice.

A field experiment was conducted at Bangaun, Lamahi-3, Dang, Nepal to study the effect of GA3 on growth and flowering attributes of African marigold (Tagetes erecta) in Inner Terai of Nepal. The experiment consists of three replications and 8 treatments and laid out in a randomized complete block design- consisting of various concentrations of GA3 viz. 0ppm, 50ppm, 100ppm, 150ppm, 200ppm, 250ppm, 300ppm, and 350ppm. Kolkata local variety of African marigold was tested. The study revealed that among different concentrations of GA3, 300ppm showed the tallest plant height (72.93cm) and the highest basal diameter (1.49cm). Maximum numbers of primary branches (3.11) and the greatest plant spread (32.11cm) were obtained from 250ppm; similarly, maximum numbers of secondary branches (13.80) were recorded in 350ppm. In the case of floral parameters both 100ppm and 350ppm recorded earlier days to 50% flowering (44.00 days each), days for 100% flowering was recorded almost similar in every treatment that sticks around 54 and 55 days, maximum diameter (5.370cm) of flowers were obtained from 50ppm, the greatest fresh weight (6.180g) was recorded in 350ppm, 250ppm showed a maximum number of flower per plant (104.13), similarly, a longer duration of flowering (58 days) was recorded in 300ppm. Among all treatments, the 250ppm level of GA3 was found to be most suitable in terms of production perspective.

Evaluation of different fungicides against rice blast was carried out in research plot of the Agronomy farm of IAAS, Prithu Technical College, Lamahi Municpality, Dang district of the Lumbini Province, inner terai region of Nepal during June to November, 2017. The objective of the experiment was to evaluate the efficiency of different chemical fungicides against rice blast. The experiment was conducted in Randomized Complete Block Design with the use of susceptible variety ‘Mansuli’. Different fungicides like Hexaconazole 5% SC (Udaan), Propiconazole 25% EC (Tilt), Captan 70% + Hexaconazole 5% WP, Validamycin 3% L, Tricyclazole 75% WP (TRIP) and Biomycin (Kasugamycin 3% S.L.) were applied five times at weekly interval with the doses of 2mL/L of H2O, 1.5mL/L of H2O, 2g/L of H2O, 2mL/L of H2O, 2g/L of H2O and 2mL/L of H2O respectively. From the result, it was concluded that all the fungicides were effective in controlling leaf blast but Tricyclazole 75% WP (TRIP) was more effective among other fungicides and untreated control plots with least leaf blast severity (27.85%), least incidence (35.5%), least mean AUDPC (64.64%) and highest grain yield (3.93 t ha-1) followed by Biomycin. It is thus concluded that fungicide Tricyclazole 75% WP should be sprayed five times at weekly interval for the management of leaf blast in rice.

Nitrogen (N) fertilizer is considered as one of the most important factors affecting growth and grain yield of hybrid maize. This study was conducted to determine the effects of different rates of nitrogen and varieties on growth and yield of hybrid maize in Lamahi Municipality, Dang, Nepal from June to October, 2019. Three levels of hybrid maize varieties (10V10, Rajkumar F1 and NMH-731) and four levels of nitrogen (160, 180, 200 and 220 kg N ha-1) were evaluated using two factorial randomized complete block design with three replications. The results showed that grain yield and yield attributing traits of hybrid maize varieties increased with the increasing level of nitrogen from 160 to 220 kg ha-1. The application of nitrogen @ 220 kg N ha-1 produced the highest grain yield (10.07 t ha-1), cob length (16.33 cm), no of rows per cob (14.97), no of grains per row (33.37), cob diameter (4.54), thousand grain weight (276.77 g), stover yield (12.91 t ha-1), biological yield (23.00 t ha-1), harvest index (43.80), gross return (NRs. 208940 ha-1), net return (NRs.104488 ha-1) and B:C ratio (2.001). The hybrid maize variety 10V10 produced the highest grain yield (9.35 t ha-1), net returns (NRs. 91740.66 ha-1) and B:C ratio (1.91) accompanied by the highest cob length (16.25 cm), and as number of grains per row (32.35) as compared to other varieties. This study suggested that maize production can be maximized by cultivating hybrid maize variety 10V10 with the use of 220 kg N ha-1 in inner Terai region of Nepal.

This experiment was conducted in the farmer’s field at Khajrauta, Gadhawa-4, Dang, Nepal to evaluate the effect of integrated nutrient management on growth and yield of cauliflower as well as their residual effects on soil properties. The cauliflower variety silvercup-60 was grown under eight different treatments; T1: 50% N through RDF + 50% N through FYM; T2: 50% N through RDF + 50% N through PM; T3: 50% N through RDF + 50% N through VC, T4: 50% N through RDF + 25% N through FYM + 25% N through PM; T5: 50% N through RDF + 25% N through VC + 25% N through PM; T6: 50% N through RDF + 25% N through VC + 25% N through FYM; T7: 50% N through RDF + 25% N through VC +25% N through FYM; T8: 50% N through RDF + 50% N through FYM,VC and poultry manure. The experiment was laid out in RCB design with three replications. The result revealed that the highest plant height (36.40 cm), number of leaves (15), plant spread (31.72 cm), leaf area (526.5 cm2), curd weight (207.3g) and curd yield (12.85 t/ha) were found under 50% N through RDF +50% N through VC. The root length, root diameter and root density were better under all INM treatments as compared to 100% N through RDF. INM treatments showed lesser bulk density, lesser particle density, greater infiltration rate and greater organic matter content than application of 100% N through RDF. Soil total nitrogen was increased in all INM treatments while soil available phosphorus decreases in all treatments except 100% N trough RDF and 50% N through RDF +50% N through PM. Thus, farmers are suggested to apply 50% N through VC along with 50% N through RDF to increase cauliflower yield.

A field experiment was conducted to evaluate the plant height, yield and yield attributes of wheat under different tillage practices and nitrogen level at Dang, Nepal during winter season 2018-19. The experiment was laid out in split plot design with two tillage practices viz. zero tillage and conventional tillage as main plot factor and four level of N viz. 50 kg ha-1, 75 kg ha-1, 100 kg ha-1and 125 kg ha-1 as sub plot factor and each replicated thrice. The result revealed that there is no significant relation between tillage practice and plant height of wheat while N level significantly affect the plant height. 125 kg N ha-1 recorded the highest plant height (110.7 cm). Zero tillage recorded the highest effective tiller m-2 (254) and grain yield (3.3 t ha-1) whereas spike length, grain spike-1, biological yield and harvest index were not significant with tillage practices. Regarding the N level, 125 kg N ha-1 recorded the highest effective spike m-2 (279), spike length (10.6 cm), grain spike-1 (48), thousand grain weight (46.3 g), grain yield (3.6 t ha-1) and biological yield (9.4 t ha-1). 50 kg N ha-1 recorded the highest harvest index (42.9%). The interaction between the tillage practice and nitrogen level showed the significant effect on grain yield and harvest index where as other parameters showed non-significant relation. The zero tillage with 125 kg N ha-1 recorded the highest grain yield (3.9 t ha-1).

A field experiment was carried out at research field of Lamjung Campus, Nepal during September 2015 to February 2016 to assess the response of cauliflower (Brassica oleracea L. var. botrytis) to different combination of nitrogenous fertilizer with Azotobacter. 6 treatment with 4 replications were laid out in Randomized Complete Block Design. Phosphorous and potassium was applied full does in all the treatments with chemical fertilizer. It was recorded that the application of recommended doses of nitrogen along with the bio-fertilizer significantly increased morphological characters and yield as compared to other treatments. Besides, the stem diameter was non-significant to the different treatments. It was followed by the full dose of NPK without azotobacter and then 50% nitrogen with azotobacter, which was statistically at par with 25% nitrogen with azotobacter, followed by FYM + Azotobacter. Curd yield along with all the morphological characters were seen lowest in control. Cauliflower curd yield at recommended dose of nitrogen did not significantly differ with the curd yield recorded at half of recommended dose of nitrogen with azotobacter. The finding demonstrated a saving of 50% of nitrogen where it can be substituted with the application of bio-fertilizer to increase the yield and morphological character.

In this work, we investigate how the assumption of chemical equilibrium with leptons affects the deconfinement phase transition to quark matter. This is done within the framework of the Chiral Mean Field model (CMF) allowing for non-zero net strangeness, corresponding to the conditions found in astrophysical scenarios. We build 3-dimensional QCD phase diagrams with temperature, baryon chemical potential, and either charge or isospin fraction or chemical potential to show how the deconfinement region collapses to a line in the special case of chemical equilibrium, such as the one established the interior of cold catalyzed neutron stars.

We investigate the phase transition from hadron to quark matter in the general case without the assumption of chemical equilibrium. The effects of net strangeness on charge and isospin fractions, chemical potentials, and temperature are studied in the context of the Chiral Mean Field (CMF) model that incorporates chiral symmetry restoration and deconfinement. The extent to which these quantities are probed during deconfinement in conditions expected to exist in protoneutron stars, binary neutron-star mergers, and heavy-ion collisions is analyzed via the construction of 3-dimensional phase diagrams.

In situ and ex situ characterization were performed to assess the effects of potassium fluoride postdeposition treatment (KF PDT) on Cu(In,Ga)Se2 (CIGS) films and solar cells. Real-time spectroscopic ellipsometry enabled the in situ observation of the modification of the CIGS dielectric function and surface roughness thickness during KF PDT. In addition, deep-level transient spectroscopies (DLTS) and deep-level optical spectroscopies and scanning-DLTS enabled the identification of the nature and location of trap levels. Two main traps were present in both films near Ev + 0.56/0.61 eV and Ev + 0.99 eV, but with clearly lower concentrations for the latter in the KF PDT film. Finally, devices were fabricated, and higher efficiencies were found for the KF PDT devices. SCAPS modeling indicates that the traps identified by deep-level spectroscopies are in part responsible for these changes.

In view of the large-scale utilization of Cu(In,Ga)Se2 (CIGS) solar cells for photovoltaic application, it is of interest not only to enhance the conversion efficiency but also to reduce the thickness of the CIGS absorber layer in order to reduce the cost and improve the solar cell manufacturing throughput. In situ and real-time spectroscopic ellipsometry (RTSE) has been used conjointly with ex situ characterizations to understand the properties of ultrathin CIGS films. This enables monitoring the growth process, analyzing the optical properties of the CIGS films during deposition, and extracting composition, film thickness, grain size, and surface roughness which can be corroborated with ex situ measurements. The fabricated devices were characterized using current voltage and quantum efficiency measurements and modeled using a 1-dimensional solar cell device simulator. An analysis of the diode parameters indicates that the efficiency of the thinnest cells was restricted not only by limited light absorption, as expected, but also by a low fill factor and open-circuit voltage, explained by an increased series resistance, reverse saturation current, and diode quality factor, associated with an increased trap density.

Nanometer-scale deep-level transient spectroscopy (nano-DLTS) is used to simultaneously map the spatial distribution of the $E_V$ + 0.47 eV trap in p-type Cu(In,Ga)Se2 with surface topography, providing a spatially resolved correlation between electrical traps with physical structure. It is demonstrated that the observed EV + 0.47 eV trap properties using nano-DLTS match those seen with conventional macroscopic device-scale DLTS measurements. Additionally, maps of the EV + 0.47 eV trap reveal that this trap is not uniformly distributed and is likely associated with specific grain boundary structures. The combined approach reveals overall trap impact from the local nanometer scale to the device (micrometer-centimeter) scale and correlation with physical structures on the nanometer-scale that can be broadly applied to any semiconductor material.

In order to understand the role of moisture ingress in the degradation of Cu(In, Ga)Se 2 solar cells, different samples were soaked in water at different stages during the fabrication of the device. The samples along with reference devices were characterized by current density-voltage (J - V) and external quantum efficiency (QE) measurements to obtain an outline of the deteriorating effect. The device performance was observed to be the worst for the water soaked CIGS thin film. Raman and Secondary ion mass spectroscopy analysis were done on the same sample. More chemical analysis will be done in the near future.

In the scale-up of Cu(In1-xGax)Se2 (CIGS) solar cell processing for large-area photovoltaics technology, the challenge is to achieve optimum values of layer thicknesses, as well as CIGS Cu stoichiometry and alloy composition x within narrow ranges and simultaneously over large areas. As a result, contactless metrologies - those that provide such information in real-time or in-line process step by step, with the capabilities of large-area mapping - are of great interest in this technology. We have demonstrated high-speed multichannel spectroscopic ellipsometry (SE) in a number of modes for CIGS metrology, including 1) single-spot real-time SE monitoring of (In1-xGax)2Se3 as the first stage in multisource evaporation of three-stage CIGS; 2) control of Cu stoichiometry in the second and third stages of the process; 3) single-spot in situ SE analysis of alloy composition and grain size averaged through the thickness for the final CIGS film; 4) offline mapping of the CIGS thickness and composition over large areas, as well as mapping after each device fabrication step for correlation with local small area cell performance; 5) ex situ single-spot analysis of alloy composition profiles in CIGS and of completed solar cell stacks to extract thicknesses and properties of semiconductor and contact layers; and 6) predictive capability for quantum efficiency based on the results of SE multilayer analysis. With the future development of new instrumentation, the offline and ex situ capabilities in multilayer analysis and mapping will be possible in-line for both rigid and roll-to-roll flexible substrates.

Rice (Oryza sativa L.) is a dominant staple food crop of Nepal which production and productivity is significantly declining compared to several years due to inappropriate nutrient management practices. A field experiment was conducted at Lamahi, Dang to evaluate the performance of hybrid rice(US-305) under rain fed condition with five precision nutrient management practices [Viz: Nutrient Expert® -Rice (NE) recommendation; Leaf Color Chart (LCC) N and Nutrient Expert (P and K); Nutrient Expert (N) and Farmers Fertilizer Practices (P and K); Farmers Fertilizer Practices (FFP) and Government Recommendation (GR)] replicated four times in RCBD design during June to October, 2018. The experimental finding showed that SSNM based Nutrient Expert® -Rice (NE) recommendation gave higher grain yield (6.36 ton ha-1) and straw yield (12.62 ton ha-1) which leads to highest gross return (NRs 242,498) and B: C ratio(3.08). Between the treatments Nutrient Expert® -Rice (NE) recommendation was excellent to growth parameters like plant height, crop growth rate, relative growth rate and leaf area index over FFP. Further, Nutrient Expert® -Rice (NE) recommendation gave significantly higher effective tiller m-2(354.50), panicle length (26.31), panicle weight (81.50), filled grain (390) and fertility (87.56%) over FFP. Nutrient Expert® -Rice (NE) recommendation has increased the grain yield by 23.97% with yield difference of 1.23 ton ha-1 and straw yield by 39.44 % with yield difference of 3.57 ton ha-1 in comparison with FFP. Hence the experiment concluded that site specific nutrient management recommendation that accounts Nutrient Expert® -Rice and leaf color chart could be the practical decision tool for making authentic fertilizer recommendation.

In this paper, we describe a model allowing for the optimization of the thickness of the anti-reflective (AR) coating for Cu (In 1−x Ga x ) Se 2 (CIGS) solar cells. This model is based on an optical model developed based on transfer matrix theory as well as accurate measurement of the dielectric function and thickness of each layer in the stack by in-situ spectroscopic ellipsometry. The thickness of the AR coating was then optimized in real time to optically enhance the performance of the device for various device configurations, including CIGS thickness and AZO thickness. The influence of the substrate temperature on the properties of the AR coating and the device was also studied.

Multi-layer anti-reflective coatings serve as excellent light traps in the red and the near infra-red regions, thereby enhances the performance of ultra-thin CIGS solar cells. In this study, the properties of different materials are explored and the scope of the layers to be used as multiple layer AR coatings are studied. A greater reduction in reflectance was observed for ultra-thin CIGS solar cells with an optimized structure. Different combinations of AR coatings were explored in order to decrease the overall reflectance of the solar cell without increasing the complexity of the cell. There was almost an increase of 8% in the short circuit density of the device with the optimized multi-layer AR structure.

Mo films were deposited on SLG substrates by sputtering to observe the influence of substrate temperature (Tss) and post-deposition annealing on film structure and alkali diffusion. The Mo films were characterized by XRD and AFM, indicating an increase of the grain size and a decrease of the roughness with Tss. After annealing, the samples deposited at 100°C show smaller grain size and higher surface roughness. Secondary ion mass spectroscopy (SIMS) analysis were also performed, and indicated a decrease of the Na and K with increased Tss, with the smallest intensity for the samples deposited at 100°C. A 3-D numerical model was used for simulating the grain boundary diffusion.

The impact of the composition of a 3-stage-process deposited CIGS on the deep level spectrum was investigated using deep level transient and optical spectroscopies to probe defects throughout the bandgap to have a complete picture of the defect spectrum. It is shown that the defect spectra depend strongly on the Ga/In ratio with both higher numbers of trap levels and higher trap concentrations (by >65%) on average in the higher Ga content films. These facts can likely explain the reduced CIGS solar cell efficiency at higher Ga content.

Alternative materials are of interest for the fabrication of thin film solar cells since they could offer potential enhancements for high efficiency devices. Cd1-xZnxS is such a material. In this preliminary study, structural and optical properties of films deposited by chemical bath deposition (CBD) for the two main compositions, ZnS and CdS, were studied. More specifically, ex-situ measurements by spectroscopic ellipsometry were performed, allowing for the analysis of the dielectric functions. GIXRD measurements were also used to assess the crystal structure for both films, indicating mixed phases for CdS, versus a single phase for ZnS, with larger grains for the CdS films.

In this study, Mo thin films were deposited on soda lime glass substrates at various temperatures using direct-current magnetron sputtering to observe the influence of substrate temperature (Tss) on Na diffusion. Tss was varied from room temperature to 200 °C. Structural analyses of the as deposited films were performed using scanning electron microscopy, atomic force microscopy and reflection measurements, while secondary ion mass spectroscopy measurements were carried out to obtain Na depth profile. Both theoretical and numerical models were used for simulating and understanding grain boundary diffusion mechanism for Na through Mo films as a function of substrate temperature.

Traps in Cu(In, Ga)Se 2 (CIGS) deposited by listage and 3-stage co-evaporation processes were characterized using conventional deep level transient and optical spectroscopies (DLTS/DLOS) and scanning-DLTS to quantity and map the deep levels associated with the different growth approaches. Two defects were observed at E V + 0.44/0.50 eV and E V + 0.97 eV. The total deep level trap concentration was found to vary primarily due to the E V + 0.97 eV trap, which was ∼4X larger in the 1-stage sample. This large increase correlates with the reduced open circuit voltage and conversion efficiency typically observed in 1-stage co-evaporation grown CIGS, suggesting that controlling the presence and concentration of this level may be important to enable high-efficiency CIGS solar cells using simpler processes.

Cu(In,Ga)Se2solar cells were fabricated using a hybrid cosputtering/evaporation process, and efficiencies as high as 12.4% were achieved. The films were characterized by energy-dispersive X-ray spectroscopy, glancing incidence X-ray diffraction, scanning electron microscopy, auger electron spectroscopy, and transmittance and reflectance spectroscopy, and their properties were compared to the ones of films deposited by coevaporation. Even though the films were relatively similar, the ones deposited by the hybrid process tend to have smaller grains with a slightly preferred orientation along the (112) axis and a rougher surface. Both types of films have uniform composition through the depth. Characterization of these films by variable angle of incidence spectroscopic ellipsometry allowed for the calculation of the position of the critical points, via calculation of the second derivative of the dielectric function and fit with critical points parabolic band oscillators. The solar cells were then characterized by current-voltage and quantum efficiency measurements. An analysis of the diode parameters indicates that the cells are mostly limited by a low fill factor, associated mostly with a high diode quality factor () and high series resistance ( ) .

Real time spectroscopic ellipsometry (RTSE) has been applied for in-situ monitoring and analysis of all three processing stages in the co-evaporation of copper indium-gallium diselenide (CuIn 1−x Ga x Se 2 ; CIGS) for high efficiency photovoltaic devices. The first stage entails indium-gallium selenide (In 1−x Ga x ) 2 Se 3 (IGS) deposition at a substrate temperature of 400°C on soda lime glass coated with opaque Mo. In this stage, an accurate deposition rate and the final IGS bulk and surface roughness layer thicknesses can be obtained. In the second stage, co-evaporation of Cu and Se converts the IGS film to CIGS at an elevated substrate temperature of 570°C. A bulk layer conversion model is justified and employed to analyze the second-stage RTSE data, resulting in steady-state IGS-to-CIGS thickness and volume fraction conversion rates. Near the end of the second stage, the formation of a Cu 2−x Se layer on the CIGS surface can be tracked in terms of an effective thickness rate. The final Cu2-xSe effective thickness at the CIGS surface is obtained in a time interval spanning the end of the second stage to the beginning of the third. Finally, in the third stage, the Cu-rich CIGS/Cu 2−x Se is converted to slightly Cu-poor CIGS by co-evaporation of In, Ga, and Se. In this stage, the thickness conversion rate, and the endpoint bulk and surface roughness layer thicknesses can be obtained. In the three stages, the thickness rates and final thicknesses yield information on the total elemental fluxes, and the roughness evolution yields information on grain growth and near-surface coalescence processes. Modeling of the dielectric functions in future studies is expected to yield compositional information and thus relative metallic fluxes. Variations in the RTSE-deduced information can yield insights into run-to-run irreproducibilities that influence the solar cell performance. The application of these capabilities in the fabrication of solar cells with thick (2.5 µm) and thin (0.3 µm) absorbers is demonstrated.

The performance of ultra-thin CIGS solar cells can be greatly improved by the addition of multilayer anti-reflective coatings. They serve as excellent light traps in the red and near infra-red regions, thereby enhancing the total efficiency of the solar cell. In this study, multiple layer AR coatings were optimized on ultra-thin CIGS solar cells and a reduction in reflectance was observed. Different materials were explored in order to decrease the overall reflectance of the solar cell without increasing the complexity of the cell.

Ultrathin Cu(In,Ga)Se 2 (CIGS) films were deposited by 1-stage, 2-stage and 3-stage co-evaporation processes. In situ, real time spectroscopic ellipsometry (RTSE) was used to study the growth dynamics of the ultrathin CIGS films. Time dependent surface roughness layer (d s ) and bulk layer (d b ) thicknesses were extracted in the early stages of film growth. Exsitu spectroscopic ellipsometry was used to characterize the fundamental optical constants of these films. Other ex-situ measurements were performed on each ultrathin layer to corroborate composition, thickness, grain size and surface roughness thickness obtained by the SE measurements.

CdS/CdTe thin film photovoltaics were produced with transition metal nitrides (TMNs) as back contacts. The devices show photovoltaic activity but a significant Schottky barrier was found at the back contact. Solar cells perform better as the ZrN films are thicker due to improved microstructure. The good reflectance of ZrN makes it acts as a reflective layer to reduce optical losses and lower the thickness of CdTe. Pure N 2 plasma treatment of the back surface of the CdTe and annealing did not improve the performance. A thin layer of Cu was introduced to dope the CdTe and completed with a ZrN film but more amount of Cu deteriorates the performance. Although the nitrides are highly stable and have good electrical properties, we have not been able to obtain devices to date that are not limited by the back contacts.

CuInSe2, CuGaSe2, and alloys thereof produced by a hybrid sputtering and evaporation method show evidence of being dopable with nitrogen by the replacement of some of the Ar sputtering gas with N2. This results in a decrease in resistivity of the films with increasing N2 pressure in the sputtering gas. No doping of AgInSe2 or CuAlSe2 has been observed to date following similar methods of deposition. The films are now being tested as back contacts to CdTe solar cells. To date only high resistance contacts have been obtained but more testing and improved CdTe cleaning techniques are required to obtain optimized contacts. The doped chalcopyrites represent potential materials for tunnel junctions for use in CIGS photovoltaics and other devices.

In this study, we have developed top side multilayer stacks as anti-reflective coatings to serve as light traps in the red and near infrared where enhanced absorption is required for solar cells with ultra-thin Cu(In1-xGax)Se2 (CIGS) absorbers. Multiple AR layers were deposited on the solar cells and large increases in short circuit current density were observed. We have explored various materials in order to reduce overall AR coating thickness (and thus complexity) for ease of manufacturing.

Alternative deposition methods and materials are of interest for the fabrication of thin film solar cells since they offer potential enhancements for either low cost, high speed or high efficiency but also because they can help in better understanding the underlying physical and chemical processes that could lead to the next generation of solar cells. Structural and optical properties of ZnS and CdS films deposited by either chemical bath deposition (CBD) or atomic layer deposition (ALD) were studied. More specifically, ex-situ measurements by spectroscopic ellipsometry as well as transmission and reflection measurements were performed, allowing for the analysis of the growth processes as a function of deposition parameters. These measurements also allowed for a parameterization of the dielectric functions of ZnS and the evolution of its grain size and band gap as a function of thickness.

In the scale up from small area solar cells to large area production modules, it is important to understand the effects of macroscopic nonuniformities in basic properties on the ultimate performance of the devices. In this study, we have spatially correlated non-uniformities in thin-absorber (~ 0.7 μm) CIGS [Cu(In1-xGax)Se2] based solar cells with the corresponding performance parameters of small area devices. Non-contacting spectroscopic ellipsometry (SE) mapping of constituent layers over a 10 cm × 10 cm area has been performed step by step during batch processing, providing CIGS composition, as well as bulk and surface roughness thickness maps for each layer of the device structure. After film stack preparation and mapping, an 18 × 9 array of 0.5-cm2-area solar cells was fabricated in order to establish a spatial correlation between the composition/ thicknesses and cell performance maps over the same area. This approach serves to characterize the inherent non-uniformities that occur during large-area, thin-layer deposition, and is uniquely suited for industrial application. In addition, given sufficient non-uniformity, correlations between layer properties, deduced by SE at different spatial points of a large area cell structure, and the solar cell performance at those points enables expeditious optimization. As an example of the application of this capability, we have demonstrated the feasibility of depositing efficient, verythin CIGS in a three stage process, designed to reduce materials cost and increase throughput of solar modules.

Real-time spectroscopic ellipsometry (RTSE) is shown to be an effective contactless probe of copper selenide thin-films used as a precursor material during 2-stage and 3-stage growth of Cu(In,Ga)Se 2 solar cells. The Cu 2−x Se thin-films were deposited by a hybrid sputtering/evaporation process onto native oxide covered Si(100) and studied by RTSE, and by complementary atomic force microscopy (AFM), X-ray diffractometry, transmission and reflection (T&R) spectrophotometry, and Hall Effect measurements. RTSE deduction of the total charge carrier densities (n), electronic scattering times (τ), fundamental energy bad-gaps (E g ), and electrical resistivities (ρ) of the Cu 2−x Se thin-films agree well with post-deposition ex-situ measurements. The RTSE measurement reveals growth mechanism and dielectric functions which ultimately reflect the electronic behavior.

Thin films of Cu(In,Ga)Se 2 with various copper contents as functions of the copper and gallium contents were deposited by co-evaporation onto thermally oxidized silicon wafer (100). In-situ Real Time Spectroscopic Ellipsometry (RTSE) is used to understand the effect of the Ga/(In+Ga) ratio and the Cu atomic % on the growth and optical properties of ultra -thin CIGS films. We have demonstrated that RTSE can be used effectively to identify the growth process and to distinguish the effects of copper from those of gallium on the surface roughness evolution and dielectric functions.

Alternative deposition methods and materials are of interest for the fabrication of thin film solar cells since they offer potential enhancements for either low cost, high speed or high efficiency but also because they can help in better understanding the underlying physical and chemical processes that could lead to the next generation of solar cells. In this study, we will present new results on the deposition of ZnS by atomic layer deposition (ALD) as an alternate to CdS deposited by chemical bath deposition.

Transparent conducting ZnO:Al (AZO) thin films were deposited by using radio frequency (RF) magnetron sputtering system and were analyzed with regards to their potential application as a window layer for CIGS solar cells. Their properties were measured in-situ and ex-situ by real time spectroscopic ellipsometry (RTSE) and were correlated with ex-situ characterization, such as AFM, XRD, and T&R measurements. As the deposition power was increased, an increase in the conductivity (via an increase by the contribution of the Drude oscillator), a reduction of the transmittance in the IR and an increase in the grain size was observed by RTSE, while the growth mechanism remained the same for all powers.

Molybdenum thin films were deposited by rf and dc magnetron sputtering and their properties analyzed with regards to their potential application as a back contact for CIGS solar cells. It is shown that both types of films tend to transition from tensile to compressive strain when the deposition pressure increases, while the conductivity and the grain size decreas. The nucleation of the films characterized byin situand real time spectroscopic ellipsometry shows that both films follow a Volmer-Weber growth, with a higher surface roughness and lower deposition rate for the rf deposited films. The electronic relaxation time was then extracted as a function of bulk layer thickness for rf and dc films by fitting each dielectric function to a Drude free-electron model combined with a broad Lorentz oscillator. The values were fitted to a conical growth mode and demonstrated that the rf-deposited films have already smaller grains than the dc films when the bulk layer thickness is 30 nm.