Advancements in Thin Crystalline Silicon Solar Cells: A Pathway to Cost-Effective Solar Energy

A recent study has made significant strides in enhancing the efficiency of thin crystalline silicon (c-Si) solar cells, potentially facilitating a more cost-effective and widespread utilization of solar energy.

Researchers have engineered a novel, multilayered architecture that markedly improves the performance of future-generation solar cells.

Solar energy has become an essential component in the global drive toward clean and sustainable energy solutions. Currently, approximately 95% of solar cells are fabricated from crystalline silicon (c-Si). Commercially available designs predominantly feature a c-Si photoactive layer with a thickness ranging from 160 to 170 micrometers. However, silicon comprises almost 50% of the overall production cost of a solar panel. Thus, experts anticipate that future c-Si solar cells will be substantially thinner.

Regrettably, despite recent advancements, the conversion efficiency of thin c-Si solar cells remains substantially inferior to that of their thicker industrial counterparts. This issue arises because current design strategies for thin c-Si cells optimize isolated parameters, such as short-circuit current density, open-circuit voltage, or fill factor. Existing methodologies do not address these variables in a holistic manner, which is crucial for achieving high efficiency.

Breakthrough Research and Technological Innovations

In this context, a research group from Hangzhou Dianzi University in China has formulated a new approach that results in significant efficiency gains for thin c-Si solar cells. Published in the Journal of Photonics for Energy, the study marks a considerable milestone in the advancement of silicon-based solar cell technologies.

The researchers employed various optical simulations and optimized certain key optical and electrical attributes responsible for the disparity in conversion efficiencies between thick and thin c-Si solar cells. They achieved this by running simulations of multiple thin cell designs using commercial software. Further empirical studies led to an inventive fabrication technique that offers multiple advantages over traditional methods.

Rather than using the conventional method of cutting silicon ingots to produce thick c-Si layers, the research team adopted a layer transfer technique. Utilizing hydrofluoric acid, they etched pores into a thick silicon wafer to create a porous substrate. They then grew a 20-micrometer-thin monocrystalline silicon layer on this substrate, which was subsequently detached and transferred onto a flexible stainless-steel base.

Performance Augmentation via Nano-Coatings

To amplify the optical and electrical attributes of the thin silicon layer, multiple metal nanofilms were deposited on both sides using plasma-enhanced chemical vapor deposition. These layers consisted of SiO2/SiNx/SiOx and Al2O3/SiNx/SiOx films with pyramidal textures on the sides facing the front and back of the solar cell, respectively.

The modifications resulted in increased light absorption in both shorter and longer wavelengths, thereby boosting the short-circuit current density. When compared with a reference standard solar cell, the current density escalated from 34.3 to 38.2 mA/cm2. Additionally, the SiO2 and Al2O3 layers furnished high surface passivation, reducing the loss and recombination of generated charge carriers. Consequently, the open-circuit voltage rose from 632 mV in the reference cell to 684 mV in the newly designed cell, while the fill factor increased from 76.2% to 80.8%.

Both simulation and experimental results confirmed that the newly proposed approach resulted in an increase in conversion efficiency from 16.5% to 21.1%, a noteworthy improvement of 4.6 percentage points, or approximately a 28% gain compared to the reference cell. This brings the thin c-Si cells close to the performance levels of their thicker industrial equivalents, currently at 24% efficiency.

According to Leonidas Palilis, Associate Editor of JPE and Professor of Condensed Matter Physics at the University of Patras, Greece, the study presents a groundbreaking approach to achieving high-performance thin crystalline silicon solar cells using significantly less silicon. Specifically, for a 20-micrometer cell, roughly one-eighth of the silicon amount needed for a thicker 160-micrometer cell is required based on the same panel dimensions.

This development is poised to significantly contribute to the cost-effective and expanded adoption of silicon solar energy technology, attributable to the reduced manufacturing costs and the associated increase in solar panel production capacity.

Reference: “Investigation on significant efficiency enhancement of thin crystalline silicon solar cells” by Guanglin Xie, Zhen Zhang, Xinshuo Han, Shengjie Ma, Yue Zang, Lu Wang, and Wensheng Yan, published on September 12, 2023, in the Journal of Photonics for Energy.
DOI: 10.1117/1.JPE.13.035501

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• Journal of Photonics for Energy
• Hangzhou Dianzi University Research
• Crystalline Silicon Solar Cells: An Overview
• Solar Cell Efficiency Records
• Sustainable Energy Technologies
• Plasma-Enhanced Chemical Vapor Deposition
• University of Patras Condensed Matter Physics
• DOI for the specific research paper