Double-sided heterojunction (HJT) photovoltaic models can pay for themselves much faster than single-sided counterparts.
HJT panels were first developed by the Japanese company Sanyo (now owned by Panasonic) in the 1980s. Since then, several manufacturers have tested and improved them to reach commercial production and reduce the dependence of the photovoltaic industry on materials such as silver, writes ecoticias.com.
Photocell models with heterojunction technology (HJT) can pay for themselves much faster than single-sided counterparts. Compared to traditional solar panels, which capture light from only one side, double-sided panels absorb light reflected from adjacent surfaces in addition to that received directly from the sun.
HJT solar cells are divided into three types and are distinguished by the material used to cover their other side: glass/glass, glass/transparent sheet and glass/opaque sheet. The first — the most effective and strongest part. However, it is also the most expensive and heaviest. Perhaps for these reasons, such photocells are not so popular, despite their efficiency, but everything can change.
Modern modules use HJT heterojunction technology and consist of two different semiconductor materials: crystalline silicon and amorphous silicon. This form of photovoltaic cell is created by applying a layer of amorphous silicon on each side of a crystalline silicon cell and has a “sandwich” form factor. Amorphous silicon has a wider band gap, allowing it to effectively trap high-energy photons, while crystalline silicon controls low-energy photons. The heterojunction of these two provides more efficient light absorption and reduces efficiency losses due to electronic recombination.
In 2020, Italian company 3Sun EGP demonstrated that double-sided heterojunction solar modules can reach and exceed 24.5% efficiency. The latest panels from companies such as China's Maysun use double-sided tempered glass and 210 mm cells capable of converting 25% of “clean” energy. In addition, Soltec algorithms increase light capture by calculating the ideal angle taking into account radiation from both sides of the module. In the latest generation modules, the HJT cell has a symmetrical front and back structure, which increases the energy output of the back section by 30% and allows a quick payback for the higher installation costs typical of double-sided panels.
In addition, the new HJT modules also are less likely to degrade over time and are generally not as sensitive to high temperatures as traditional solar panels, enabling manufacturers to offer multi-year warranties.
Next-generation double-sided solar cells may be particularly in demand where the angle of incidence of sunlight is extremely small, or where the coating has high reflective properties. For example, the sand of the desert, the white roof of the factory, etc. Such devices will be useful in agriculture, especially for crops with the potential to use sunlight passing through glass.