Abstracts:Photovoltaic (PV) modules in desert environments benefit from higher irradiation levels and, therefore, better energy yield. However, higher irradiation leads to higher temperature and higher electrical losses in module interconnections, which could influence the lifetime and energy yield of PV modules. The electrical losses in module interconnection act as heat sources. The interconnections’ electrical properties are also affected by solar cell temperature. In this paper, we simulate and evaluate the performance of the interaction between thermal and electrical losses in module interconnections and the influence of tab on module power and temperature. We compare the impact of tab losses on module power and temperature under different irradiation and ambient temperature levels, as well as compare the module in Qatar and Germany as desert and moderate climates. We show that the thermal influence of tab on module power is maximum 0.8%_rel compared to a module without any thermal influence from tab, which, in this case, are the thermal coefficients of the tab and temperate elevation due to joule heating. This change is 0.2%_rel and 0.6%_rel for Qatar and Germany during one year, respectively. As a solution for desert applications, apart from full-cell layout, we have evaluated modules with half-cell design due to increased optical gains and reduced electrical losses. We determined the optimum tab width for the modules with half-cell and full-cell design and for two to five busbars under normal operating cell temperature (NOCT) conditions. We show that in NOCT conditions, the optimized tab width on half-cell modules is almost half of the tab width for full-cell modules. Furthermore, the temperature of half-cell modules is always less than that of full-cell modules for the similar tab widths. By considering the optimum tab width for half-cell and full-cell modules, - n average increase of 0.2 °C is simulated, which is due to the higher active area and narrower tabs and, thus, higher irradiance and thermal loads.

Abstracts:This paper aims to study the ac electrical response of standard-thick, ultrathin, and passivated ultrathin Cu(In,Ga)Se₂ (CIGS) solar cells. Ultrathin CIGS is desired to reduce production costs of CIGS solar cells. Equivalent circuits for modeling the behavior of each type of solar cells in ac regime are based on admittance measurements. It is of the utmost importance to understand the ac electrical behavior of each device, as the electrical behavior of ultrathin and passivated ultrathin CIGS devices is yet to be fully understood. The analysis shows a simpler ac equivalent circuit for the ultrathin device without passivation layer, which might be explained by the lowered bulk recombination for thin-film CIGS solar cells when compared with reference thick ones. Moreover, it is observed an increase in shunt resistance for the passivated ultrathin device, which strengthens the importance of passivation for shunts mitigation when compared with unpassivated devices.

Abstracts:Cu(In,Ga)Se₂ (CIGS)-based photovoltaic cells were fabricated under varying deposition conditions for the Mo back contact and CIGS absorber layers. Specifically, O₂ concentration and sputtering pressure were varied during the Mo deposition, as well as the final Mo-layer thickness. The maximum deposition temperature was then varied during the subsequent deposition of the CIGS-layer by thermal coevaporation. The <italic>JV</italic> response curve of the finished devices were recorded and used to calculate the usual solar performance characteristics (efficiency, <italic>J</italic>_sc, <italic>V</italic>_oc, fill-factor, <italic>R</italic>_oc, and <italic>R</italic>_sc). The effects of the varied fabrication conditions on these characteristics were then investigated, and CIGS-deposition temperature alone was found to have had a significant influence on <italic>J</italic>_sc. Following this, the entire <italic>JV</italic>-curve was analyzed using functional data analysis (FDA). The curve shape was revealed to be affected not only by temperature, but by O₂ conc. and Mo sputter pressure as well. The effect of these fabrication parameters was greatest in regions of the curve larger than <italic>V</italic>_oc. External quantum efficiency measurements on the finished devices were also studied using FDA, indicating a strong influence of temperature in reducing collection across most of the visible spectrum. Mechanisms that aim to explain these observations are proposed. This work details, according to the authors&#x2019; best knowledge, the first-ever use of FDA in the analysis of photovoltaic devices.

Abstracts:The main advantages of the organic&#x2013;inorganic halide perovskite solar cell technology are high efficiencies achieved after short development time in combination with rather simple solution-based processing. In this paper, we address remaining challenges by presenting a low-temperature two-step hybrid evaporation-spincoating method that combines high reproducibility with easy fabrication and high stabilized efficiencies, which is compatible with the processing of pervoskite silicon tandem solar cells and avoids using hazardous solvents such as dimethylformamide and dimethylsulfoxide. Lead iodide (PbI₂) is thermally evaporated and subsequently converted into a compact crystalline perovskite layer by methylammonium iodide spincoating. Moreover, the role of the interface passivation between perovskite absorber and electron transport layer on crystallization and optoelectronic properties of the perovskite absorber is investigated within a systematic thickness and concentration variation of [6, 6]-phenyl-C₆₁-butyric acid methyl ester passivation layer and by analyzing charge extraction with spatial and time resolved photoluminescence measurements. With an optimized charge extraction, 18.2&#x0025; stabilized efficiency under one sun illumination is achieved. This is the highest value reported so far for the single junction perovskite solar cells made by a two-step hybrid evaporation-spincoating method.

Abstracts:Currently, one of the main limitations in ultrathin Cu(In,Ga)Se₂ (CIGS) solar cells are the optical losses, since the absorber layer is thinner than the light optical path. Hence, light management, including rear optical reflection, and light trapping is needed. In this paper, we focus on increasing the rear optical reflection. For this, a novel structure based on having a metal interlayer in between the Mo rear contact and the rear passivation layer is presented. In total, eight different metallic interlayers are compared. For the whole series, the passivation layer is aluminum oxide (Al₂O₃). The interlayers are used to enhance the reflectivity of the rear contact and thereby increasing the amount of light reflected back into the absorber. In order to understand the effects of the interlayer in the solar cell performance both from optical and&#x002F;or electrical point of view, optical simulations were performed together with fabrication and electrical measurements. Optical simulations results are compared with current density&#x2013;voltage (<italic>J&#x2013;V</italic>) behavior and external quantum efficiency measurements. A detailed comparison between all the interlayers is done, in order to identify the material with the greatest potential to be used as a rear reflective layer for ultrathin CIGS solar cells and to establish fabrication challenges. The Ti-W alloy is a promising a rear reflective layer since it provides solar cells with light to power conversion efficiency values of 9.9&#x0025;, which is 2.2&#x0025; (abs) higher than the passivated ultrathin sample and 3.7&#x0025; (abs) higher than the unpassivated ultrathin reference sample.

Abstracts:Unlike conventional photovoltaic (PV) modules that generate power by absorbing light through the front side only, a bifacial PV module can generate power by absorbing light through the rear as well as the front, which would lead to an enhancement of power generation. Particularly, bifacial PV modules would have the advantage of lower power loss in shaded environments than monofacial PV modules, thanks to the light absorbed through the rear side. To predict the power of a bifacial PV module in a shaded environment, modeling is suggested by considering the shaded areas, the operational status of the bypass diodes, and the temperature of the bifacial PV module. To verify the power prediction of a bifacial PV module with a shaded area, modeled and measured powers are compared, showing error rates of 7.28&#x0025;. From the results of the power loss experiments for bifacial and monofacial PV modules in shaded environments, it is confirmed that the bifacial PV module shows a relatively low power loss rate when compared with the monofacial PV module, with a power loss rate being 87.26&#x0025; of the rate for the monofacial PV module.

Abstracts:In research on photovoltaic (PV) device degradation, current&#x2013;voltage (<inline-formula><tex-math notation="LaTeX">$I$</tex-math></inline-formula>&#x2013;<inline-formula><tex-math notation="LaTeX">$V$</tex-math></inline-formula>) datasets carry a large amount of information in addition to the maximum power point. Performance parameters such as short-circuit current, open-circuit voltage, shunt resistance, series resistance, and fill factor are essential for diagnosing the performance and degradation of solar cells and modules. To enable the scaling of <inline-formula><tex-math notation="LaTeX">$I$</tex-math></inline-formula>&#x2013;<inline-formula><tex-math notation="LaTeX">$V$</tex-math></inline-formula> studies to millions of <inline-formula><tex-math notation="LaTeX">$I$</tex-math></inline-formula>&#x2013;<inline-formula><tex-math notation="LaTeX">$V$</tex-math></inline-formula> curves, we have developed a data-driven method to extract <inline-formula><tex-math notation="LaTeX">$I$</tex-math></inline-formula>&#x2013;<inline-formula><tex-math notation="LaTeX">$V$</tex-math></inline-formula> curve parameters and distributed this method as an open-source package in R. In contrast with the traditional practice of fitting the diode equation to <inline-formula><tex-math notation="LaTeX">$I$</tex-math></inline-formula>&#x2013;<inline-formula><tex-math notation="LaTeX">$V$</tex-math></inline-formula> curves individually, which requires solving a transcendental equation, this data-driven method can be applied to large volumes of <inline-formula><tex-math notation="LaTeX">$I$</tex-math></inline-formula>&#x2013;<inline-formula><tex-math notation="LaTeX">$V$</tex-math></inline-formula> data in a short time. Our data-driven feature extraction technique is tested on <inline-formula><tex-math notation="LaTeX">$I$</tex-math></inline-formula>&#x2013;<inline-formula><tex-math nota- ion="LaTeX">$V$</tex-math></inline-formula> curves generated with the single-diode model and applied to <inline-formula><tex-math notation="LaTeX">$I$</tex-math></inline-formula>&#x2013;<inline-formula><tex-math notation="LaTeX">$V$</tex-math></inline-formula> curves with different data point densities collected from three different sources. This method has a high repeatability for extracting <inline-formula><tex-math notation="LaTeX">$I$</tex-math></inline-formula>&#x2013;<inline-formula><tex-math notation="LaTeX">$V$</tex-math></inline-formula> features, without requiring knowledge of the device or expected parameters to be input by the researcher. We also demonstrate how this method can be applied to large datasets and accommodates nonstandard <inline-formula><tex-math notation="LaTeX">$I$</tex-math></inline-formula>&#x2013;<inline-formula><tex-math notation="LaTeX">$V$</tex-math></inline-formula> curves including those showing artifacts of connection problems or shading where bypass diode activation produces multiple &#x201C;steps.&#x201D; These features together make the data-driven <inline-formula><tex-math notation="LaTeX">$I$</tex-math></inline-formula>&#x2013;<inline-formula><tex-math notation="LaTeX">$V$</tex-math></inline-formula> feature extraction method ideal for evaluating time-series <inline-formula><tex-math notation="LaTeX">$I$</tex-math></inline-formula>&#x2013;<inline-formula><tex-math notation="LaTeX">$V$</tex-math></inline-formula> data and analyzing power degradation mechanisms in PV modules through cross comparisons of the extracted parameters.

Abstracts:A common method of measuring the temperature of a photovoltaic module is by attaching a sensor to its back surface. However, since this method of measurement is punctual, the temperature gradient along the module surface is not considered. In addition to that, the temperature of the sensor is usually considered equal to the temperature of the photovoltaic cells, thus ignoring the temperature drop along the materials in between. This paper focuses on the problem of computing the average cell temperature of photovoltaic modules, based on information available on their respective datasheets and on measurements of the open-circuit voltage and solar irradiance. For that, different methods regarding identification and translation of the single-diode model parameters are used in conjunction, aiming to establish a simple and accurate procedure for computing the average temperature. The best performing combinations are then compared with IEC-60904-5, which presents a procedure for calculating the equivalent cell temperature of a module. Such computing procedures for the average module temperature have been experimentally tested, presenting coherent results.

Abstracts:Most of the photovoltaic (PV) models involve mainly the reproduction of the nonlinear <italic>I</italic>&#x2013;<italic>V</italic> curves for PV modules with a certain degree of accuracy. Previous researches have used equivalent circuits based on common electronic devices to model the real behavior of PV modules, such as the single and double diode models. Unfortunately, those models are static, i.e., they can reproduce the <italic>I</italic>&#x2013;<italic>V</italic> curve of a PV module for a specific environmental condition (fixed irradiance and temperature). As consequence, different models should be obtained for each different environmental condition, restricting the use of the models for a limited set of irradiance and temperature values. The first contribution of this paper is the proposition of an irradiance and temperature dependent double-diode model for PV modules. In this model, the internal parameters depend on the environmental conditions, extrapolating its use for temperature and irradiance values different from those the parameters were initially estimated. In addition, two parameter estimation techniques are proposed for this new model. The techniques use a combination of analytical equations and numerical optimization based on the pattern search algorithm. Comparison results based on experimental <italic>I</italic>&#x2013;<italic>V</italic> curves of real PV modules are presented in order to prove the accuracy of the model and techniques.