Thin Film Is Not the Budget Option Any More: What CdTe and Perovskite Mean for India's Next 100 GW

Executive Summary

India added 27 GW of solar in the first half of 2026, up 49% year on year, taking cumulative solar capacity to 164.8 GW by 30 June. Utility-scale projects hold 83% of that base; rooftop holds 17%.

At this pace, the next 100 GW arrives faster than most DISCOM planning cycles assume. So the technology choices being made in tender documents right now will shape network behaviour for the next 25 years.

Which brings me to thin film. A reader sent me a popular explainer on thin film panels, and it repeats the description I still hear in review meetings: flexible, cheap, 7–13% efficient, short-lived, fine for niche uses. That picture is roughly a decade out of date.

A commercial cadmium telluride (CdTe) module today is rated at up to 19.7% efficiency and 550 W, carries a 25-year linear performance warranty with 0.3% warranted annual degradation, and is manufactured at a 3.3 GW per year plant in Sriperumbudur, Tamil Nadu. That is not a niche product. It is a mainstream utility-scale module with a domestic supply chain.

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What Thin Film Actually Is

The name describes the construction, not the quality. Instead of slicing wafers from a silicon ingot, the semiconductor is deposited as a layer a few micrometres thick onto glass or a flexible substrate. Less material, fewer process steps, far less energy per watt.

Four families matter, and they are not equal:

Organic PV also exists, but it is a research and specialty-application story, not a procurement option.

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The Claims That Need Correcting

Because these myths still drive decisions, let me take them one at a time.

One claim in that explainer does hold up, and it matters in India: thin film handles heat and partial shading better. CdTe has a gentler temperature coefficient, so on a 46°C afternoon in Bihar or Rajasthan the gap between nameplate and delivered power is smaller.

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Why This Matters More in India Than Elsewhere

Nameplate efficiency is a datasheet metric. Energy yield is the business metric.

What a DISCOM or a C&I buyer actually pays for is kWh delivered per kWp installed per year, over 25 years, at a given site. Three Indian conditions push that calculation toward CdTe more than a European one would:

1. Heat. Module temperatures routinely sit 25–30°C above ambient. A better temperature coefficient converts directly into afternoon generation, which is exactly when our evening ramp begins to build.
2. Humidity and spectrum. In the humid Gangetic belt, diffuse light is a large share of annual irradiance. Thin film's response to diffuse and low light narrows the gap further.
3. Soiling and partial shading. Dust and partial shade are facts of life here, not edge cases.

Then there is policy. ALMM List-II for domestic solar cells took effect on 1 June 2026, and the PLI scheme is funding more than 10 GW of polysilicon capacity. Domestic content is no longer a preference, it is a gate. A technology with a large Indian plant already running clears that gate today rather than in a future quarter.

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Where Thin Film Still Loses

I would be doing you no favours by selling this in one direction.

• Constrained rooftops. When the roof is the binding constraint and you need maximum kW on limited square metres, higher-efficiency silicon wins. Most residential and many C&I rooftops fall here.
• Supplier concentration. The CdTe market is dominated by a single large manufacturer. Procurement teams should price that concentration as a risk.
• Financing familiarity. Lenders and insurers know crystalline silicon. Anything else invites extra diligence, which costs time.
• End-of-life handling. Cadmium is a heavy metal. The leading manufacturer runs a recycling programme, but if you buy it, write the take-back obligation into the contract rather than assuming it.

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Perovskite: The Real Disruption, With a Caveat

In July 2026, LONGi reported a 35.5% silicon-perovskite tandem cell, certified by ESTI, and 34.3% at 261 cm². For context, a single-junction silicon cell runs into a theoretical ceiling near 29%. Tandems break through it by stacking a perovskite layer that harvests the blue end of the spectrum above a silicon cell that takes the red.

That is a genuine step change in the physics of what a square metre can deliver.

The caveat is the one every materials engineer repeats: stability. Perovskites degrade under heat, moisture and UV faster than silicon does, and the field data under Indian conditions is thin. Lab records and 25-year bankable warranties are separated by a long encapsulation and reliability programme.

My working position: track perovskite closely, procure CdTe and silicon today, and write your long-term land and evacuation plans so a higher-density module can be swapped in later. Land, transmission connectivity and civil structures outlive modules.

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What This Means for Leaders

1. Tender on energy yield, not module efficiency. Specify kWh/kWp/year at the site's temperature and irradiance profile, with a performance guarantee, instead of a minimum efficiency percentage that quietly excludes a whole technology class.
2. Model the afternoon, not the annual average. Evaluate how each technology behaves at 2 p.m. in May, because that is where the evening ramp risk begins.
3. Treat ALMM and domestic content as design inputs, not a paperwork step at the end of the process.
4. Price supplier concentration and end-of-life explicitly, with take-back obligations written into the contract.
5. Keep a perovskite watch item on the technology agenda, reviewed every six months, with stability data, not records, as the criterion.

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Key Takeaways

• India is at 164.8 GW of solar, having added 27 GW in H1 2026; technology decisions now lock in 25-year outcomes.
• Thin film's old reputation — 7–13% efficient, short-lived — is outdated: leading CdTe is 19.7%, 550 W, 25-year warranty, made in Tamil Nadu.
• India's heat, diffuse light and soiling make energy yield the right metric, and that narrows the gap further.
• Thin film still loses on constrained rooftops, and it carries supplier concentration and end-of-life considerations.
• Perovskite tandems at 35.5% are the real disruption. Stability, not efficiency, is the gating question.

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Randhir Verma is an enterprise leader in digital transformation and smart metering, working with utility platforms at the scale of millions of endpoints. The views here are personal.

Sources: pv-tech / Mercom: India adds record 27 GW solar in H1 2026; First Solar Series 7 (India); LONGi: 35.5% silicon-perovskite tandem cell, ESTI-certified. Written in response to "Thin Film Solar Panels" on Web Stories Shares.