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| Home > Publications database > Silicon heterojunction solar cells on thin wafers – prospects in different utilization scenarios |
| Book/Dissertation / PhD Thesis | FZJ-2026-04302 |
2026
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
Jülich
ISBN: 978-3-95806-999-2
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Please use a persistent id in citations: doi:10.34734/FZJ-2026-04302
Abstract: The urgent need to address climate change has accelerated the global transition from fossil fuels to renewable energy sources, with photovoltaics (PV) emerging as the fastest-growing technology in this field. By 2023, PV systems accounted for three-quarters of newly installedrenewable energy systems, highlighting their central role in meeting global climate targets. Among PV technologies, crystalline silicon (c-Si) solar cells dominate the market due to their high efficiency, with silicon heterojunction (SHJ) solar cells demonstrating particularly strong potential. However, the transition to sustainable energy solutions requires strategies to reduce material usage, lower costs, and enhance the energy return on investment (ERoI). Reducing silicon wafer thickness has emerged as a promising approach, as theoretical studiespredict high efficiencies for wafers in the 79–110 μm range. Despite the promise of thinner wafers, their experimental performance under diverse scenarios remains insufficiently explored, particularly for applications in tandem solar cells, indoor lighting, and module integration. This thesis systematically investigates the performance of thin wafer based SHJ solar cells under these different utilization scenarios, addressing the challenges and opportunities. In the first part of this work, the impact of wafer thickness on the performance of singlejunction SHJ solar cells was examined experimentally. Here, several SHJ solar cells of wafer thicknesses ranging from 60 to 170 μm were studied and their performance compared to theoretical predictions. In line with theoretical predictions, the implied open circuit voltage (iVOC) was observed to increase as the wafer thickness reduced with some cells approaching the fundamental limit. However, contrary to predictions, the implied fill factor (iFF) was observed to reduce for thinner wafers due to the increased effect of surface recombination. Additionally, the short circuit current density (JSC) was observed to reduce for thinner cells due to increased infrared light loss. The tradeoff majorly between the gains in VOC and losses in JSC resulted in a broad range of comparable high efficiency for cells between 75 μm and 170 μm. In the second part of this work, the use of thin SHJ solar cells as bottom cells in perovskitesilicon tandem configurations was studied. Taking into considerations the major losses associated with thinner cells (surface recombination and infrared light loss), the potentials of increased passivation and light management were explored. Solar cells of wafer thicknesses of 80 μm and 135 μm were compared under standard AM1.5G and perovskitefiltered spectra. Under AM1.5G, thicker passivating layers improved passivation resulting in peak VOC values of 747 mV for 80 μm cells and 741 mV for 135 μm cells. However, thicker passivation increased series resistance and parasitic absorption which resulted in lower efficiency compared to the standard passivation. Between wafer thicknesses, efficiency reduced slightly with thinner wafers, as the best 80 μm and 135 μm cells achieved efficiencies of 23.3% and 23.8%, respectively. However, under the perovskite-filtered spectrum, the effect of parasitic absorption was minimized due to the absence of short wavelength light under bottom cell conditions. Despite a 40% reduction in wafer thickness, the bottom-cell efficiency decreased only by 0.35%abs under the perovskite-filtered spectrum. Light management improvements, including an ITO/MgF2/Ag back reflector and MgF2 anti-reflection coating, resulted in enhanced JSC . The back reflector increased JSC by 0.58 mA/cm² for 80 μm cells and 0.52 mA/cm² for 135 μm cells, while the anti-reflection coating added ~0.3 mA/cm² across all cells. In the third part of this thesis, the performance of thin SHJ solar cells under indoor lighting conditions, such as low light and LED illumination, which are relevant for applications in Internet of Things (IoT) devices, was studied. SHJ solar cells with thicknesses of 80 μm, 100 μm, 130 μm, and 170 μm under both solar and LED illumination demonstrated generally better open-circuit voltage, fill factor, and efficiency in the 80 μm and 100 μm cells under typical indoor conditions (250 – 500 LUX). While the 80 μm cells produced less power than the theoretically optimal 1.8 μm cells, they offered practical advantages due to their enhanced durability. In the final part of this thesis, the transition of thin-wafer SHJ cells into modules was investigated, emphasizing laser cutting optimization, grid design, and mini-module performance. Laser cutting parameter sets were evaluated, with the optimized set achieving higher VOC, FF, and overall efficiency, particularly for 80 μm cells. Grid design optimization further improved efficiency by reducing shading losses and series resistance, achieving a 0.6%abs efficiency gain. Mini-modules fabricated with 80 μm and 135 μm wafers showed no clear trends related to wafer thickness, as resistive losses introduced during soldering process overshadowed intrinsic thickness differences.
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