By Vasanthi Sreeram, Chief Technical Officer, Websol Energy System Limited
In solar cell manufacturing, the worst time to think about the next technology transition is after you have already committed your capital to the current one. The industry has moved through conventional mono-crystalline, multi-crystalline, Mono-PERC, and now TOPCon. Each transition has caught manufacturers off guard – not because they lacked technical awareness, but because their manufacturing infrastructure was built without the flexibility to absorb what came next. That is the problem worth solving, and one the industry as a whole has not yet reckoned with seriously enough.
The technology cycle is compressing
In the initial days, a cell technology would dominate for a decade or more before the next one took over. That cycle is shortening. PERC’s primacy in India lasted roughly three to five years before TOPCon began displacing it. Back contact technology, which places all cell contacts on the rear, eliminating front-side shading losses and pushing efficiency ceilings higher, is already being discussed seriously as the next transition, even as most Indian manufacturers are still mid-way through their TOPCon upgrade.
This is not alarmism. TOPCon is a sound, well-reasoned choice for India right now and will remain the dominant cell architecture for the foreseeable future. The capital cost is approximately $40 million per GW compared to $70 million per GW for HJT, and the transition pathway from PERC is relatively manageable – it builds on existing n-type silicon processing with incremental additions rather than a wholesale retooling. Back contact, by contrast, requires an entirely different set of tooling, significantly more complex process steps, and manufacturing yields are still being stabilised at commercial scale globally. But the window to prepare for what comes after TOPCon is open right now – precisely because back contact is not yet here.
The hidden problem of utilisation
Before discussing technology flexibility, there is a more immediate concern that deserves candid attention: the gap between installed capacity and what that capacity actually delivers. A great deal of India’s solar manufacturing conversation is dominated by GW-scale announcements. Far less attention is paid to what happens after commissioning. In cell and module manufacturing specifically, capacity utilisation and yield are two telling indicators of operational maturity. Ideally, a well-run line should operate at capacity utilisation above 90 per cent, with yield in the range of 96 to 97 per cent. In practice, most companies are achieving the required yield — but the significant variation lies in capacity utilisation. A considerable number of facilities, particularly in module manufacturing, are operating at only 70 to 80 per cent utilisation. That is not a marginal difference: it represents a substantial cost and output gap that no amount of additional announced capacity can compensate for. A similar scenario will arise when all the announced cell capacity becomes operational, and that is a challenge the industry would do well to anticipate now rather than discover later.
This matters for the flexibility discussion because a manufacturing facility that is still struggling to master its current technology is in no position to absorb a future one. Flexibility is not a design feature you can bolt on to an underperforming line. It has to be earned through operational discipline first.
The case for designing in flexibility
For facilities that do have their operations under control, the next question is whether the physical design of the line anticipates what comes next. Here is what most capacity expansion announcements do not address: how the production line is physically laid out, and whether that layout has been designed with future equipment insertion in mind. Clean room dimensions, utility infrastructure routing, equipment bay spacing, power supply headroom – these decisions, made at the point of construction, determine how quickly and cheaply a facility can absorb the next technology generation.
The logic is straightforward. TOPCon can, in principle, be migrated toward back contact architecture over time. The passivating contact structure that TOPCon uses can be moved to the rear of the cell and combined with a full back-contact design, and this is the direction several global equipment suppliers are already engineering toward. If your facility layout has been designed with that insertion point in mind, the capital cost of the next transition drops significantly. If it has not, you are looking at a far more disruptive and expensive overhaul.
A brownfield upgrade done on a thoughtfully designed line is fundamentally different from one attempted on a line that was never built with change in mind. The former is a targeted insertion; the latter is closer to a rebuild.
Knowledge transfer as strategic infrastructure
There is a dimension of technology transition that rarely features in public discourse but is arguably more consequential than equipment selection: the depth of process knowledge that a manufacturing team has genuinely internalised. Installing new equipment is the easy part. What takes time, and what determines whether a facility can sustain high performance through a technology transition, is the transfer of process understanding from equipment suppliers to the operating team. Structured knowledge transfer arrangements, where suppliers commit to an extended period of hands-on operational support, are not a nicety. They are a prerequisite for building the kind of manufacturing resilience that allows a facility to adapt independently when the next shift arrives.
The difference between a team that has truly absorbed a process and one that remains dependent on external support to keep the line running is the difference between a facility that can evolve and one that cannot. India’s solar manufacturing ambition will only be realised if the knowledge embedded in these facilities is domestic, deep, and transferable across technology generations.
Phased expansion as strategic tool
There is one more principle worth stating directly: phasing is not indecision. It is risk management. When capacity is committed in one large tranche on a single technology assumption, the manufacturer is fully exposed to the risk that the landscape shifts before the facility reaches full utilisation. When capacity is phased, the second tranche benefits from the learning of the first, from better technology visibility, and from the ability to make different equipment choices if conditions have changed.
This is particularly relevant for India right now, as a wave of large-scale announcements moves toward execution. The manufacturers who will be best positioned in 2030 are not necessarily those who announced the most capacity in 2025, they are the ones who built their facilities with the discipline to absorb what they do not yet know is coming.
The solar industry has always been driven by those who could see the next curve before it arrived. Designing for that next curve – in the layout of the facility, in the depth of technical capability, in the structure of expansion – is where the real competitive advantage is built.
