The aim of this work is to present the development and comparison of thin n + pp + industrial bifacial silicon solar cells produced with the local screen-printed Al back surface field (BSF) to those with the selective BSF doped with aluminum-boron. To produce solar cells with selective BSF, the boron diffusion based on spin-on dopant was introduced in the process sequence. The thin SiO 2 layer (10 nm) thermally grown did not produce good passivation on the rear face and wafers were contaminated during aluminum diffusion in the belt furnace. The implementation of selectively doped BSF improved the efficiency by reflecting minority charge carriers and the wafer contamination by belt furnace was compensated by boron diffusion. The bifacial solar cells with B-Al selective BSF achieved an efficiency of 13.7% / 8.9% (front / rear illumination) and presented lower sensitivity to the belt furnace processing and to the quality of the rear surface passivation.

The PERC solar cell family is manufactured by the industry because the passivation of both faces can improve the efficiency. The passivation and anti-reflective (AR) coating is usually performed using silicon nitride. However, the silicon dioxide may produce a good passivation in the emitter and in the boron BSF. The goal of this paper is to present the analysis of the TiO2 AR coating in PERT solar cells passivated with SiO2. Based on previous studies, the dry oxidation was performed at 800 °C and 860 °C, growing the SiO2 layer on the phosphorus emitter of 50 nm and 60 nm, respectively. The thickness of the TiO2 AR coating evaporated by ebeam technique was optimized and the SiO2/TiO2 double layer was analyzed by the comparison of the electrical parameters and internal quantum efficiency of the PERT solar cells and the reflectance of the double layer. The efficiency of 16.8 % was achieved with 37 nm TiO2 coating and SiO2 layer grown at 800 ºC. The firing of the conductive pastes reduced the thickness of the SiO2/TiO2 layer and the lowest weighted average reflectance was 2.8 %. The solar cells with thinner TiO2 coat presented low internal quantum efficiency in wavelengths higher than 700 nm.

In quantitative analysis, instrument stability is a mandatory requirement. The stability of resolution, sensitivity and gain versus count rate, temperature and time are the key considerations in instrument performance. A careful study of the stability of an x-ray spectrometry system consisting of an x-ray detector and digital spectroscopy analyser was performed. As a new approach, resolution and throughput are presented versus dead time. To test the stability of resolution, gain and sensitivity versus time, hundreds of spectra were acquired over almost 4 days. The average resolution was 179.9 eV (RSD 0.67%). The gain variation during this experiment was found to be 0.13 eV at the 5.895 keV Mn Ka. The uncertainty contribution of the detector on the peak intensity was found to be RSD 0.0651%. The gain and sensitivity data showed a very small trend with changing ambient temperature. The experiment was repeated at constant ambient temperature, concluding that no statistically significant drift of peak intensity could be observed in that condition.

Abstract:In this paper we discuss ways to obtain information about the quality of ground water and their availability. We classify the different approaches in two categories: geophysical methods, e.g., electroresistivity sounding, seismic survey, gravimetry, MT (magnetotelluric) method, and geochemical methods. The former ones are able to provide information on the geological structure, meaning depth, range, amount of water and possible connections among different exploration areas or regions at risk due to contamination. On the other hand, the last ones provide information about the quality of water and the possible of use for agriculture, industry or human consumption. As a case study we aim at the Guarani Aquifer, more specifically at its recharge zone on the southern rim.

The aim of this paper is to evaluate three grid connected photovoltaic systems that were implemented in rural properties dedicated to the animal protein supply chain in the west of the State of Paraná, Brazil. PV modules with mono and multicrystalline Si solar cells from the same supplier were used. One of the PV arrays was ground mounted, faced to North, 18 ° tilted and the others were mounted on the north-facing rooftop of the farm buildings. On the roof of a cow-shed, PV modules were 18° tilted, azimuth angle of 9° NE and on the roof of a poultry house, PV array was 13° tilted (same slope of the roof) and with an azimuth of 52° NE. Two inverter brands were applied and two approaches to connect to the electrical grid were used. The results indicated that high difference in performance ratio and yield can be produced due to the position of the inverter inside the farm (distance to the main electric input) and the installation approach. The highest performance ratio (PR) was obtained for rooftop mounted with optimum slope angle, reaching an annual PR of 86 %. This PV array installed in an approximately 8 m high cow-shed presented the lower operating temperatures due to the high wind speed on the roof. Concerning the module temperature, the higher PV module effective temperatures were observed in ground-mounted array, that achieved and annual PR of 82 %. The worst average PR obtained was 69 %, in a farm where the inverter is located near the PV array but far away from the main electrical panel.