PERC vs TOPCon vs HJT: Solar Cell Technology Compared

PERC, TOPCon, and HJT describe three different generations of silicon solar cell design, each a genuine technical improvement over the last, not interchangeable marketing labels. Understanding what separates them helps when a quote lists one specifically and the difference in price is not obviously explained.

What is PERC, and why is it still common?

PERC (Passivated Emitter and Rear Cell) is a P-type silicon cell design that added a reflective rear layer to capture more light than older standard cells, becoming the dominant mainstream technology for roughly the last decade. It remains widely available and typically the least expensive of the three technologies, a reasonable choice for a home with generous, unconstrained roof area where squeezing maximum efficiency per panel matters less.

What does TOPCon actually improve on?

TOPCon (Tunnel Oxide Passivated Contact) uses N-type silicon, which generally achieves higher efficiency and a better (lower) temperature coefficient than P-type PERC cells, meaning less output loss as the panel heats up in Singapore's consistent tropical sun. TOPCon has become the new mainstream standard for recent installations, priced moderately above PERC but increasingly close as manufacturing scale has grown.

What makes HJT different, and is it worth the premium?

HJT (Heterojunction Technology) combines crystalline silicon with thin amorphous silicon layers, generally delivering the highest efficiency and lowest temperature coefficient among the three, meaning it retains more of its rated output as rooftop temperatures climb to the 55 to 70°C common on a Singapore roof in direct sun. This makes HJT most relevant for a roof-area-constrained home, a smaller semi-detached roof half constrained on two sides, for example, where maximising generation per available square metre genuinely outweighs the higher upfront cost per individual panel.

How much does the price premium actually compound across the three technologies?

Each step up tends to add a modest, not dramatic, premium on top of the last, so the total gap between entry-level PERC and premium HJT is bigger than any single step suggests in isolation. Within the commonly cited S$1,000 to S$1,600 per kWp installed range covered in solar panel cost by system size, cell technology is one contributor to where a specific quote lands within that range, alongside brand reputation, mounting complexity, and installer overhead, rather than being the sole factor separating a genuinely low quote from a genuinely high one on paper.

Does this overlap with AIKO's ABC panel technology?

Not directly, ABC (back-contact) is a separate cell architecture change, covered in AIKO ABC panels and N-type technology, that can be combined with N-type silicon for further efficiency gains. PERC, TOPCon, and HJT describe the cell's front-and-rear junction design; back-contact describes where the electrical connections sit on the cell. The two classifications are not mutually exclusive.

What does a real installation using this generation of cell technology actually look like?

Every one of Sunnify's documented residential installations uses black monocrystalline panels, the cell family that PERC, TOPCon, and HJT all sit within as successive refinements. A specific example, the AIKO NEOSTAR panels at Tai Keng Avenue, layers N-type silicon and back-contact cell design together, illustrating how these generational improvements combine in a real, commissioned Singapore system rather than remaining a purely theoretical comparison between datasheet figures.

Does degradation rate actually differ meaningfully between the three technologies?

Somewhat, and it favours the newer N-type designs. Older P-type PERC cells are more susceptible to light-induced degradation, a specific mechanism that erodes output faster in the cell's early years, while N-type TOPCon and HJT cells are inherently more resistant to it.

SERIS, based at NUS, conducts Singapore-specific solar degradation research precisely because tropical field conditions stress panels differently than the standardised lab tests behind a manufacturer's published warranty figures. In practice, this means a TOPCon or HJT panel's real-world degradation curve over 25 years tends to track its warranty figure somewhat more closely than an older PERC panel's does, though PERC remains a perfectly reasonable choice within its own, still-solid warranty terms.

How should a homeowner actually decide between them?

Start from roof area and budget, not brand preference. A home with ample roof area and a tighter budget is well served by PERC or TOPCon.

A roof-area-constrained home able to pay a premium for maximum output per panel is the clearest case for HJT. Check the specific temperature coefficient figure on any quoted panel's datasheet regardless of technology name, covered in solar panels and Singapore heat, since specifications vary even within the same technology category across manufacturers.

Run the Sunnify solar estimate to see the actual roof area available for a specific home, the real starting point for this whole decision.