Reliability of Solar PV Modules

December 02, 2025. By News Bureau

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Vijay Kumar

Heterojunction Technology (HJT)

TOPCon technology

Renewable energy

Scientists worldwide have been chasing a target referred to as the “Holy Grail”, where solar PV becomes equal to or even less costly than fossil fuels. The prices of solar energy have been constantly dropping, more vigorously in recent years, due to significant technological advancements. It has crossed the inflexion point in the price–time curve and has now become more affordable and definitely less expensive than the energy derived from coal and oil.

However, there must be a deeper understanding in terms of usage, lifespan, and upkeep, all of which play a significant role in determining the true cost of solar PV. PV modules, the basic building blocks for harnessing solar energy, must perform for more than 30 years, delivering over 90 percent of their initial power output for most of that duration. The overall costing and investment assumptions are based on this premise. The entire economics and costing revolve around the basic assumption of crystalline modules surviving for more than 25 to 30 years.

This requires a very robust design and manufacturing of all the modules to be used in a solar farm. Any quality degradation can lead to a severe loss of power output. Consequently, the return on investment is greatly reduced. While this is well understood by several investors and decision-makers, there still exists a large grey area, and greater clarity is required in this field.

Domestic Manufacturing Landscape

As of September 2025, India’s module manufacturing capacity stands at about 110 GW and has around 27 GW of solar cell manufacturing capacity, of which around 18 GW is listed in ALMM List-II for solar cells. At present, TOPCon technology is leading, whereas PERC is gradually fading. There are efforts toward Heterojunction Technology (HJT), but due to cost considerations and the fact that its 25-year reliability is still not proven, it has not yet gained widespread acceptance. Its thin-film nature also makes it more vulnerable.

Thin-film technologies are currently not in active market use and are likely to be phased out. Examples include:

CdTe (Cadmium Telluride): Used by companies like First Solar, with efficiencies around 19–22 percent.
CIGS (Copper Indium Gallium Selenide): Also falling behind.
Perovskite Solar Cells: An emerging technology with lab efficiencies exceeding 29 percent, and tandem configurations reaching 33.9 percent. It shows great potential, especially when combined with TOPCon and HJT in tandem cell formats exceeding 30 percent.
Interdigitated Back Contact (IBC): Offers efficiencies above 25 percent, but requires complex manufacturing. It is expected to gain a niche market share and shows promise for long-term success.

Current Trends and Future Directions

High-efficiency cells like TOPCon are now scaling commercially, with efficiencies approaching 26 percent. Perovskite-silicon tandem cells are nearing market readiness and aim to achieve efficiencies over 30 percent; however, their long-term stability is still an unresolved issue.

There is growing emphasis on sustainability, such as reducing carbon footprints, recycling of PV modules, and replacing toxic materials like lead in perovskites. The adoption of AI and IoT technologies is helping optimise manufacturing processes and system performance, while IoT enables real-time monitoring of solar farms.

Other emerging technologies, such as quantum dot solar cells and organic PV, are still in early research stages but offer potential for ultra-low-cost and flexible applications in the future.

Reliability of Modules

For all types of PV modules, reliability remains the most critical parameter. A PV module must perform for 25–30 years under open and often harsh environmental conditions, which vary significantly across different geographies. The module is expected to deliver the rated power with limited degradation throughout its service life.

Even small reductions in performance can result in significant losses in energy output and therefore in revenues. Modules are exposed to external conditions like wind, temperature fluctuations, and water, which can lead to performance degradation. Therefore, the design quality, manufacturing accuracy, and the Bill of Materials (BoM) play a vital role in determining the long-term performance of a solar module.

With current technology, TOPCon cell-based modules can be made highly reliable, capable of delivering power with minimal degradation over 25 years or more.

Module Design and Types

Solar cells must be hermetically sealed and then interconnected in series and parallel configurations to form a solar PV module. A single PV module, as a basic unit of power conversion, is expected to last at least 25 years in open environments. Most modules come with a warranty ensuring performance degradation does not exceed specified limits over 25–30 years.

There are primarily two types of modules:

Crystalline Silicon-Based Modules: These include multicrystalline, PERC, TOPCon, bifacial, back-contact, and tandem cell-based modules. Currently, TOPCon cell-based modules are the most widely used.
Thin-Film Modules: These use a thin layer of semiconductor material on a glass substrate. Early versions, like amorphous silicon-based modules, were only warranted for 15 years. Now, HJT modules are more prevalent, combining crystalline silicon with thin-film layers. Tandem modules using perovskite cells also fall into this category.

The fundamental design of any module aims to protect internal cell components from environmental factors such as humidity, temperature, UV radiation, rain, and wind.

Environmental Factors for Degradation
Moisture is one of the most damaging elements for PV modules. It can degrade conductive silicon deposits, thin oxide layers, and other semiconductor layers, including poly or amorphous films. Studies have shown that effects like snail trails, corrosion, and discolouration result primarily from moisture ingress.

The quality of the backsheet and the effectiveness of sealing determine how resistant a module is to moisture penetration. Initially, backsheets were made with a Tedlar-Aluminium-Tedlar (TAT) configuration. While this design was excellent for moisture resistance due to the aluminium layer, it became less popular because:

Aluminium is conductive, making it unsuitable for high-wattage modules used in large-scale solar farms.
Although aluminium offers perfect moisture barrier properties, the added cost made it commercially less viable.

As the industry pushed for cost reduction, the use of less conforming (and sometimes less reliable) backsheets became more common. However, in large solar farms where performance guarantees are critical, the choice of a high-quality backsheet remains an important decision.

Reliability Certification

Various international standards like IEC, UL, and JIS are designed to provide third-party certifications regarding the useful life of PV modules. These tests are conducted in laboratory conditions over limited timeframes and then extrapolated to predict long-term performance. However, it’s important to understand that these certifications do not guarantee actual field performance over 25–30 years.

Modules in the real world are exposed to a combination of stress factors – temperature, humidity, UV radiation, wind, and light – which change over time. Manufacturer reliability labs often conduct Design of Experiments (DoE) under fixed conditions to test module durability under combined stress scenarios.

Such testing helps in estimating the real-world life and performance variation of PV modules made from different materials and technologies. In this context, the backsheet remains one of the most crucial components to monitor and evaluate.

- Vijay Kumar, COO of Zuvay Technologies Pvt. Ltd.