India's solar sector is transitioning between three cell architectures, and that shift itself represents the investment opportunity.
The architecture transition
Three years ago, PERC was the consensus architecture — proven, bankable, cost-effective. By 2024 the equation had shifted: TOPCon captured the volume tier while HJT began claiming the premium segment. Manufacturers still operating PERC at scale by FY27 face not just efficiency disadvantages but competitive exclusion from major tenders.
PERC's hard limit stems from rear-surface recombination — a theoretical maximum near 24.5%, with commercial lines at 22–23%. No engineering pathway exceeds this within the PERC framework. TOPCon addresses it with a 1.5 nm tunnel oxide, delivering 24–26% efficiency at capex within 20–30% of PERC's cost. HJT extends further — amorphous silicon on both surfaces, 26–27.5% efficiency, superior temperature performance — but demands entirely new lines and more than double the silver per watt.
