Understanding the Challenges and Potential of SHJ Technology

Silicon heterojunction solar cells (SHJ), also known as HIT cells, have garnered significant attention in the solar industry due to their unique properties and potential for improved performance. By utilizing passivating contacts based on a layer stack of intrinsic and doped amorphous silicon, SHJ cells boast superior surface passivation quality, holding the record for open-circuit voltage at one sun of 750 mV.

Recent advancements in carrier transport and interface carrier recombination have led to substantial improvements in the fill factor of SHJ cells. However, these cells face certain challenges, such as parasitic absorption in the front layer stack, resulting in a lower short-circuit current compared to cells with a diffused emitter. Potential solutions include using interdigitated back contact (IBC) cell structures or incorporating SHJ structures as the bottom cell in silicon-based tandem cells where parasitic absorption of blue light is not an issue.

One of the most significant technological hurdles for SHJ cells is the inability to use processes with temperatures above 200°C after the deposition of the amorphous silicon layer. This limitation excludes the use of well-established fired screen-printed metal contacts, necessitating alternative routes such as low-temperature pastes or plated contacts.

For SHJ technology to gain mainstream adoption, several challenges must be addressed, including:

1. Higher cost of tools for cell production: Establishing high-throughput fabrication lines that can compete with current standard production lines is essential to lower costs.
2. Reduction of silver usage or replacement with copper: Developing copper-plating technology can help minimize silver consumption and reduce production costs.
3. Reduction of indium usage in the transparent conductive oxide (TCO) layer: Finding alternative materials or processes can help decrease reliance on indium, further reducing costs.

If the solar industry can overcome these challenges, SHJ technology has the potential to revolutionize solar cell performance, making solar energy even more accessible and efficient. With ongoing research and development, we may soon witness the widespread adoption of SHJ cells, paving the way for a brighter and more sustainable future.