What are TOPCon solar panels?

Most radio amateurs are interested in building their own DIY off grid solar power source and so am I. TOPCon, short for Tunnel Oxide Passivated Contact, is an advanced solar cell technology that improves efficiency and energy yield compared to traditional solar panels. TOPCon solar panels use a thin passivating tunnel oxide layer to enhance carrier selectivity and reduce contact resistance, thereby allowing more sunlight to be converted to electricity. Older solar cell technology was PERC (Passivated Emitter and Rear Cell), which uses a passivated layer on the back of the cell. Both belong to the group of crystalline silicon solar cells. Efficiency of energy conversion from solar light energy to electrical energy in photovoltaic cells is said to be above 22% for TOPCon cells while it is 18-19% for PERC cells.

A research paper published in 2023 cites highest efficiency achieved as 26.4% while the theoretical maximum limit is 28.7% efficiency. TOPCon cells are n-type, meaning they are silicon cells doped with phosphorus, which gives them a negative charge. All radio amateurs will be familiar with n-type which is used in NPN and PNP transistors. The passivated layer reflects sunlight which has passed through the solar cell, thereby increasing exposure. This is useful in low light periods and in shaded regions. That is how it increases efficiency of solar light energy conversion.