Chinese researchers develop highly efficient solar cell with nanocrystalline-silicon hole contact layer

A Chinese solar technology company has developed a new type of solar cell that could revolutionize the world’s transition towards renewable energy. This breakthrough was made possible through advanced modeling by researchers at TU Delft. The new solar cell, which is made of the same material as 95% of all current solar cells, has an impressive efficiency rate of 26.81%. The research was published in Nature Energy on May 4, and it confirms the critical role that solar cells play in the energy transition.

The breakthrough was achieved through a collaboration between LONGi Green Energy Technology Co., Ltd, Sun Yat-Sen University, and Delft University of Technology. The team optimized the solar cell’s design by incorporating a new “nanocrystalline-silicon hole contact layer,” which has been a theoretical possibility for some time but had not been successfully implemented until now.

This new layer facilitates the transfer of electricity with much less resistance, resulting in higher power conversion efficiency than any other type of solar cell made from crystalline silicon. LONGi developed this new technology on standard, industry-grade silicon wafers, making it readily applicable in the production of solar panels.

Compared to previous technologies, this cell’s improved performance is significant, representing an absolute leap forward in conversion efficiency of 1.5%. Xixiang Xu, vice president of LONGi Central R&D Institute, stated that this breakthrough surpasses the performance of all other crystalline silicon solar cell architectures to date, accounting for more than 95% of solar cells produced worldwide.

Beyond surface passivation

The scientists at SYSU played a crucial role in the breakthrough by studying the flow of electricity through the new layers. By analyzing cells with and without the new layers, they discovered that cells with the layers conducted electricity better due to a low activation energy when positioned correctly. The researchers also demonstrated that highly passivated silicon heterojunction solar cells can have significantly improved fill factor and power conversion efficiency due to the high quality of surface passivation.

Professor Pingqi Gao of SYSU stated that their work on studying silicon hole contact layers with low activation energy is timely and important. The research represents a significant advance in exploring the electrical performance of hole contacts, benefiting heterojunctions, hybrids, and all silicon-based solar cells. The new solar cell architecture developed by LONGi accelerates the energy transition with the deployment of more efficient photovoltaic modules.

Advanced modeling by researchers at TU Delft played a pivotal role in realizing the innovation by detailing the energy barriers across the interfaces forming the rear-junction of the LONGi solar cell. The team analyzed the collection path of holes across the interfaces, which explained the device’s outstanding performance. Postdoctoral researcher Paul Procel stated that witnessing in real and large area devices what was theoretically predicted to be the best combination of material properties for hole-contact layers was great. Professor Olindo Isabella added that LONGi’s mastery of ultra-thin layers deposition with fine control of their opto-electrical properties is stunning and that modeling their solar cells pushes the boundary of what is meant by ideal crystalline silicon devices.

Source: Delft University of Technology

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