The economic benefit of a 12.8 kWp photovoltaic (PV) system was calculated using real consumption and production data for a typical modern single-family house in Sweden for the six years from 2019 to 2024. Electricity trade prices were based on the local spot market plus taxes and fees. The effect of a tax reduction on exported energy was evaluated. The economic benefit was simulated for the case of a virtual AC-coupled battery added to the house using a charging strategy to maximize the self-consumption of the house. Additionally, the economic benefit was simulated for a range of different yearly consumptions and PV system sizes. The calculation shows that the PV system alone can be economically beneficial, while adding a battery with typical investment prices from 2025 does not pay off if it is only used to increase the self-consumption rate.

Making good electrical contacts when interconnecting solar cells with no or very small busbars in a module can be challenging. Light beam induced current (LBIC) mapping reveals the contact quality with a high spatial resolution when evaluating the phase shift between the pulsating laser light and the current. In this research, we have fabricated solar modules with Sticky Solar Power’s “The Tape SolutionTM” and assessed the modules using LBIC phase mapping. Enhanced LBIC phase shifts correlate with smaller series resistances between the point of illumination and current extraction. The areas with abrupt changes in the phase shift were observed under optical microscope and revealed breakage or weakening along fingers. We also developed a cross-section preparation method to investigate the physical contact between the solar cell and the taped wires at the areas of interest. This method included cutting the laminated module using rotary diamond blades followed by grinding and polishing the surface to remove the damaging effects of cutting pressure. Optical microscopic and SEM/EDS images of the cross-section near the silver pads at areas with higher resistance showed low silver content in some parts and minor gaps between the silver and solder alloy.

After installation of a PV system, the question arises if it works correctly. Comparing the yield with some prediction gives a hint if the system is OK, but takes a long time and depends on the weather during that period. Also the effect of shading by trees or buildings is hard to estimate and often not included in the prediction. We present a solution based on the evaluation of the power curve of the PV system from a sunny day. The peak power of the PV system is obtained by simulating this power curve using the peak power as a fit parameter. The simulation uses the public library pvlib python including the clear sky model of Ineichen and Perez, and a database for the air turbidity. The temperature of the PV modules is calculated from air temperature and wind speed. The software with its graphical user interface for Microsoft Windows is freely available. The simulation of irradiance and module temperature is compared to experimental data. As an example, the peak power of some newly installed PV systems was evaluated. Furthermore, a degradation analysis of the peak power over a 10-year period of a test system is performed.

Research on the structural defects of silicon such as grain boundaries and dislocations, their spatial distributionand how they impact the resulting solar cell  performance often proceed by polishing the sample, etching toreveal the dislocations and grain boundaries, and then scanning the surface to image the defects and recordtheir corresponding positions. While a lot of work has been devoted to developing appropriate etches and howto correlate the etch pits to cell performance, materials pertaining to preparation of samples for defect etching, which is a crucial step to ensure successful imaging and analysis, are limited. This work describes a methodof polishing multicrystalline silicon solar cell samples in preparation for defect etching. The method described herein:

- Utilizes both mechanical and chemical mechanical polishing.

- Can be applied to both fabricated silicon solar cells and as-cut wafers.

Having a photovoltaic (PV) system raises the question of whether it runs as expected.Measuring its energy yield takes a long time and the result still contains uncertainties from varyingweather conditions and possible shading of the modules. Here, a free software PVcheck to measurethe peak power of the system is announced, using the power data of a single sunny day. The softwareloads a data file of the generated power as a function of time from this day. This data file is providedby typical inverters. The software then simulates this power curve using known parameters like angleand location of the PV system. The assumed peak power of the simulation can then be adjusted sothat the simulated curve matches the measured one. The software runs under Microsoft Windows™and makes use of the free library pvlib python. The simulation can be refined by importing weatherdata like temperature, wind speed, and insolation. Furthermore, curves describing the nominalmodule efficiency as a function of the illumination intensity as well as the power-dependent inverterefficiency can be included in the simulation. First results reveal a good agreement of the simulationwith experimental data. The software can be used to detect strong problems in PV systems afterinstallation and to monitor their long-time operation.

Herein, a method to quantify the amount of reduction in the internal quantumefficiency (IQE) of multicrystalline silicon solar cells that can be attributed to grainboundaries is presented. By correlating the IQE maps obtained via light beaminduced current (LBIC) topography with optical images of Secco-etched samples,the distribution of IQE values at the positions of grain boundaries can be comparedwith the distribution of IQE values for all other positions where other defects mayexist. The segmentation of IQE at 826 nm maps of the samples shows grainboundaries to be more detrimental compared with the combined effects of all otherdefects that may exist in other regions of the cell. The grain boundaries reduce theaverage IQE by up to 4.07% absolute for the cell from the bottom of the ingot.

In this work, we investigated the Si pre-amorphization implantation (PAI) assisted low temperatureannealing process to activate boron implantation in n-Si in a hydride vapor phase epitaxy (HVPE) reactor, which canbe used for the Si subcell fabrication in the III-V/Si tandem solar cells enabled by the corrugated epitaxial lateralovergrowth (CELOG). A uniform boron activation in Si and a low emitter sheet resistance of 77 /sq was obtained atannealing temperatures of 600-700°C. High-resolution x-ray diffraction was used to study the recrystallization ofamorphous silicon and the incorporation of boron dopants in Si. Hall measurements revealed p-type carrierconcentrations in the order of 1020 cm-3. The n-Si wafers with B implantation activated at 700°C by HVPE wereprocessed to solar cells and characterized by the standard light-current-voltage measurement under AM1.5 spectrumand external quantum efficiency measurements. The developed B implantation and low temperature activationprocesses are applied to the InP/Si seed template preparation for CELOG, on which CELOG GaInP over a Si subcellwith a direct heterojunction was demonstrated.

Crystal defects such as grain boundaries affect the overall performance of a solar cell. The light beam induced current method allows for the localized quantification of the impact on the internal quantum efficiency of such defects. This work presents a method to estimate the separate impact of grain boundaries on the internal quantum efficiency (IQE) of multicrystalline silicon solar cells by correlating LBIC topographs with optical images of etched samples. Segmenting the impact of the grain boundaries on the IQE against those of other defects in our samples showed that the grain boundaries remain the most detrimental. The average IQE at 826 nm was reduced by up to 1.29 % (vs 0.25 % for other defects) absolute for standard multicrystalline and up to 1.15 % (vs 0.28 % for other defects) absolute for high performance multicrystalline silicon.

In this work, we applied internal quantum efficiency mapping to study the recombination activity of grain boundaries in High Performance Multicrystalline Silicon under different processing conditions. Wafers were divided into groups and underwent different thermal processing, consisting of phosphorus diffusion gettering and surface passivation with hydrogen rich layers. After these thermal treatments, wafers were processed into heterojunction with intrinsic thin layer solar cells. Light Beam Induced Current and Electron Backscatter Diffraction were applied to analyse the influence of thermal treatment during standard solar cell processing on different types of grain boundaries. The results show that after cell processing, most random-angle grain boundaries in the material are well passivated, but small-angle grain boundaries are not well passivated. Special cases of coincidence site lattice grain boundaries with high recombination activity are also found. Based on micro-X-ray fluorescence measurements, a change in the contamination level is suggested as the reason behind their increased activity.

Wafers from a hybrid silicon ingot seeded in part for High Performance Multicrystalline, in part for a quasi-mono structure, are studied in terms of the effect of gettering and hydrogenation on their final Internal Quantum Efficiency.The wafers are thermally processed in different groups – gettered and hydrogenated. Afterwards, a low temperature heterojunction with intrinsic thin layer cell process is applied to minimize the impact of temperature. Such procedure made it possible to study the effect of different processing steps on dislocation clusters in the material using the Light Beam Induced Current technique with a high spatial resolution. The dislocation densities are measuredusing automatic image recognition on polished and etched samples. The dislocation recombination strengths are obtained by a correlation of the IQE with the dislocation density according to the Donolato model. Different clusters are compared after different process steps. The results show that for the middle of the ingot, the gettering step can increase the recombination strength of dislocations by one order of magnitude. A subsequent passivation with layers containing hydrogen can lead to a decrease in the recombination strength to levels lower than in ungettered samples.