The impedance of solar cells can be leveraged for a variety of innovative applications. However, for the continued advancement of such applications, it is crucial to understand how the impedance varies during practical operation. This work characterizes the impedance of modern crystalline silicon solar cells across different bias voltages and under varying illumination and temperature conditions. It is found that for a given bias voltage, variations in temperature have a notably stronger impact on PN junction impedance than changes in irradiance. However, during maximum power point (MPP) tracking, variations in irradiance have a larger influence on the PN junction impedance than temperature variations. This is related to the shifting operating voltage during operation. Furthermore, it is shown that the capacitance during practical operation can strongly vary for different solar cells. For instance, the areal MPP capacitance values of the two cells tested in this study at 0.1 sun irradiance and a temperature of 30 °C were 0.283 μF/cm2 and 20.2 μF/cm2, a 71-fold difference. Conversely, the range of the MPP diffusion resistance was found to be highly similar for different cells. The results of this study enhance the understanding of solar-cell impedance and have a broad applicability.@en

Visible light communication (VLC) is a promising complement considering the rising radio frequency spectrum congestion. However, photodiode receivers degrade rapidly under high ambient light (>200 W/m²). Photovoltaic (PV) cells, designed for outdoor applications, offer an effective alternative. This work studies the fundamental relationship between various LEDs and seven commercial crystalline silicon (c-Si) PV cell architectures to assess simultaneous energy harvesting and communication. The results reveal that increased PV output inversely affects bandwidth. The impact of PV cell architecture on bandwidth is mainly due to bulk doping concentration and metallization design. Higher doping reduces bandwidth at short circuit but increases it at higher operating voltages. At the transmitter end, higher irradiance levels enhance communication, but this effect is minimal at the PV maximum power point (MPP). Additionally, LED color has a negligible impact on PV cell bandwidth. The highest bandwidth is 215 kHz for Al-BSF(5”) under short-circuit, while the lowest is 0.1 kHz for SHJ at MPP. Among the tested c-Si PV architectures, Al-BSF cells exhibit the best communication stability – from 100 kHz to 10 kHz, while SHJ shows the worst – from 100 kHz to 0.1 kHz. TOPCon demonstrates the optimal balance between energy harvesting and communication for Pareto optimality.

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Reconfigurable photovoltaic modules are a promising approach to improve the energy yield of partially shaded systems. So far, the feasibility of this concept has been evaluated through simulations or simplified experiments. In this work, we analyse the outdoor performance of a full-scale prototype of a series-parallel photovoltaic module with six reconfigurable blocks. Over a 4-month-long period, its performance was compared to a reference photovoltaic module with static interconnections and six bypass diodes. The results show that under partial shading, the reconfigurable module produced 10.2% more energy than the reference module. In contrast, under uniform illumination the energy yield of the reconfigurable PV module was 1.9% lower due to the additional losses introduced by its switching matrix. Finally, a modification in the reconfiguration algorithm is proposed to reduce the output current–voltage range of the module and simplify the design of module-level power converters while limiting the shading tolerance loss.

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To achieve a high performance in sub-module power conditioning circuits, it is important that power converters are designed in accordance with the photovoltaic (PV) cell impedance at the input. Taking this one step further, exploiting the impedance of cell strings could even support novel power conditioning approaches in PV modules. In this work, we characterize the impedance of eight single-cell laminates based on different industrial c-Si PV cell architectures. This characterization is carried out by impedance spectroscopy in dark conditions at room temperature, and the capacitive and inductive effects are evaluated through equivalent model fitting. By comparing the results for the different laminates, it is revealed how the cell design affects its impedance. Our experiments show that the PN junction capacitance at maximum power point varies for the different cells between 0.30 and 45.6 μF/cm². The two main factors contributing to a high PV cell capacitance at maximum power point are (i) a low wafer dopant concentration and (ii) a high maximum power point voltage. In high-efficiency c-Si PV cells that will be fabricated in the coming years, increasing capacitances are expected for operation near the maximum power point. Furthermore, the single-cell laminates exhibit inductances between 63 and 130 nH, and our results indicate that the inductance is mostly affected by the number of busbars and the geometry of the metal contacts.

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This paper presents the fundamental study on the relationship between LED light sources and the performance of solar cell as receivers in visible light communication (VLC) links. Here, different colors of LEDs are modulated with a sinusoidal signal, and the bandwidth of the VLC system based on various c-Si PV architectures is characterized at different bias voltages. The preliminary results show that the bandwidth of such VLC system is highly influenced by the bias voltage, where higher bias voltage leads to lower bandwidth. This means that there is a trade-off between energy harvesting and communication performance when solar cells are used as VLC receivers. Meanwhile, we also observed that the bandwidth decreases as the LED irradiance level increases, and the color of LED (currently red and blue LEDs are characterized) does not pose a significant impact on the bandwidth. The highest bandwidth is found at 50 kHz for a VLC system using a 6-in TOPCON solar cell under 100 W/m2 with 100 mV bias voltage.@en

The integration of photovoltaic (PV) technology in urban environments poses new challenges for the design of PV modules. In particular, the poor shading tolerance of conventional PV modules strongly limits the energy performance of urban PV systems. In this work, we analyze how interdigitated back-contact solar cells with low-breakdown voltages can help improve the shading tolerance of PV modules. Through detailed simulations, we show that the breakdown voltage can be tuned without significantly degrading the efficiency of the solar cell. Simulation results indicate that, under partial shading conditions, cells with a 0.3-V breakdown voltage could boost by 20% the annual yield of conventional crystalline silicon PV modules with three bypass diodes. These findings are supported by a four-month-long monitoring campaign of PV modules with different breakdown characteristics, which shows a specific yield gain of about 4% in PV modules with six bypass diodes.

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Photovoltaic modules in the urban environment are very often exposed to uneven illumination conditions. The electrical interconnection between solar cells in a photovoltaic module limits the power that a solar module can generate under partial shading conditions. In this article, we introduce a PV module that is able to dynamically reconfigure the interconnection between its solar cells to minimise conduction and mismatch losses according to the irradiance distribution on its surface. Using an accurate simulation framework, it is determined that a reconfigurable PV module can generate over 12% more energy than a standard PV module with fixed topology and six bypass diodes, and as much energy as a fixed series-parallel module with six parallel strings, but at significantly lower currents. Simulation results are validated experimentally using a photovoltaic module with six reconfigurable blocks of cells controlled by a switching matrix on a high-performance solar flash simulator.@en