Researchers Find Solution for Shunting in Perovskite-Silicon Tandem Cells

A thin lithium fluoride layer was inserted to mitigate shunting

October 25, 2023


Researchers at the University of North Carolina at Chapel Hill and the Arizona State University have discovered a method to help reduce the shunting issue mainly found in perovskite-silicon tandem solar cells.

Perovskite silicon tandems are used to absorb high-energy light, with a silicon-made bottom cell specifically for absorbing lower-energy infrared rays, making their application popular in solar energy generation.

However, the main challenge for upscaling perovskite-silicon tandems is the non-uniformity of perovskites across large areas of tandem cells, which can cause shunting. This is a significant issue when large-area tandems are fabricated through a solution process.

The new method helps make large tandem cells on silicon wafers using a blading process that is still compatible with industry standards.

Crystalline silicon (c-Si) photovoltaic (PV) technology has dominated the PV market due to its increasing efficiency and decreasing costs, especially in the last two decades amidst advancing renewable energy technologies as it allows for efficient energy conversion.

However, the power conversion efficiency of silicon cells has reached a theoretical limit, making it important to transition single-junction silicon PV technology to tandems to surpass it. The transition requires the tandem technology to demonstrate high efficiency, manufacturability, and long-term stability akin to silicon.

While few existing studies have reported using Czochralski (CZ) c-Si to make efficient tandems, there are still no reports of large-area tandem fabrication employing CZ c-Si as bottom solar cells. The new study published by the researchers aims to address that.

The team inserted a lithium fluoride interlayer, significantly reducing the electricity shunting issue for large-area tandems when deposited on the hole transport layer side. This further decreased local current drains and improved interfacial contact at the perovskite interface.

Through this, they were able to stabilize the power conversion efficiency of 25.1% achieved for tandem devices with a larger aperture area of 24 sq cm.

In July 2023, researchers at the King Abdullah University of Science and Technology achieved 30% efficiency for tandem silicon-perovskite solar cells, surpassing the efficiency milestone.

Scientists at the National Centre for Photovoltaic Research and Education of the Indian Institute of Technology Bombay claimed to have achieved a power conversion efficiency of more than 26% for a four terminal-silicon perovskite tandem solar cell.