Stephen Gibbs of Ossila writes that a vital scientific paradox is often being overlooked – solar panels are less efficient as they get hotter.
October 23, 2026
In this contributed blog, Stephen Gibbs, scientific content writer at Ossila, a manufacturer with a focus on research into renewable energy, explains the physics behind heat’s negative effect on solar generation and calls for renewed focus on making the technology more climate resilient.
Following this year’s sweltering summer, government data shows nearly 172,000 solar installations have been fitted across the UK since the start of 2026. Record-breaking and back-to-back heatwaves have scorched much of Europe this year, with England recording its highest peak, 38.1°C since records began.
It is a common assumption that blazing hot, sunny days equal peak solar output; therefore, the conversation around solar energy usually revolves around expansion. However, a vital scientific paradox is often being overlooked – solar panels are less efficient as they get hotter.
As temperatures rise, grid demand spikes due to widespread air conditioning usage. Simultaneously, the net capacity of regional solar fleets drops significantly. Beyond this drop in efficiency, the long-term effects of elongated thermal cycles pose a physical threat to climate targets, permanent hardware damage, and degradation.
The primary driver of this long-term damage is the mechanical stress caused by daily temperature swings. Similar to a freeze thaw effect, the daily shift of temperature from blistering daytime heat to cooler night-time temperatures causes the different materials within a panel to expand and contact at unequal rates. Over time, this persistent thermal cycling disrupts the flow of electricity within the silicon wafers by creating microscopic fractures.
On top of this, extreme heat can lead to destabilisation in protective polymer layers. This leads to delamination, where the encapsulant layers peel away and expose the solar panels' internal components. Once exposed, ambient degradation caused by moisture causes corrosion of key internal components and leads to irreversible power failure.
The panels themselves are not the only pieces of vital grid infrastructure at risk. Higher daily temperatures also pose a threat to central and string inverters, which convert harvested energy into usable electricity. Higher ambient environments increase the operation strain on these inverters, to prevent their sensitive internal electronics from melting an automated protective mechanism is deployed. Thermal derating automatically throttles the power output to protect the internal electronics; however, this comes at cost of causing a clean energy distribution bottleneck right when the grid requires it the most.
To understand why extreme heat can negatively impact solar performance, one must look at the underlying physics of photovoltaic (PV) cells. Standard testing conditions (STC) evaluate solar panel performance at a strict cell temperature of 25°C.
Once ambient temperatures soar during a heatwave, internal cell temperature of a solar panel can be approximately 25°C to 35°C higher than the ambient air temperature and can easily exceed 65°C. For every Degree Celsius above that baseline, a solar panel loses efficiency due to its temperature coefficient:
Voltage Drop: As semiconductor temperatures rise, so does the internal energy of electrons. This reduces the cell’s open circuit voltage, causing power output to plummet.
Efficiency Loss: The typical crystalline silicon panels have a temperature coefficient of roughly -0.3°C to -0.5°C per °C. This means that during higher heats, like the 38.1°C English record peak, actual power generation can drop by 15-20% compared to the modules rated capacity.
Thanks in large part to its abundance, silicon is the most common semiconductor material used in solar cell production. However, the upper limit of efficiency for silicon has hovered at around 29%, an efficiency which worsens in elevated temperatures.
In comparison to silicon, perovskite solar cells show remarkable energy conversion efficiencies (PCEs), economical manufacturing methods, and adjustable optoelectronic characteristics. Perovskite is much better at absorbing light than traditional crystalline silicon, and it is 'tunable' to use a wider range of the solar spectrum that remains inaccessible to silicon photovoltaics. Despite the benefits, there are challenges that researchers must overcome.
For materials, such as perovskites, to be seen as viable for use in commercial solar panels, researchers must test their stability under several external stresses. Some examples of this are thermal cycling, damp heat, UV light, and light induced degradation. Silicon currently meets all the standards needed but falls short in terms of efficiency. On the flipside, perovskites show much higher potential in terms of efficiency, but by nature are susceptible to degradation caused by external factors such as temperature and humidity. On top of this, to enhance their performance and retain stability, perovskites need to be ultrathin, which further exacerbates stability issues when met with external stresses.
For any new solar materials, researchers must ensure they can withstand the same, or even tougher conditions as their silicon counterparts.
Researchers around the world have been experimenting with different ways of bringing perovskite solar cells to the commercial market:
Encapsulated Single Layer Perovskite Solar Cells (PSCs) – These cells primarily have a single active layer, meaning they can be cheaper to produce due to simpler manufacturing processes. However, encapsulated perovskite solar cells typically fall short of the 30% energy conversion efficiency mark, meaning the long-term stability of perovskite materials remains a challenge. Improving encapsulation will be vital in improving the commercial viability of PSCs.
Tandem Perovskite-Silicon Solar Cells – By combining perovskite and silicon layers, researchers have been able to break the 30% energy efficiency barrier. The perovskite layer captures higher-energy light, while the silicon layer absorbs lower-energy light, thus creating tandem cells that absorb a broader spectrum of light while proving far more stable at elevated temperatures.
While new ground is regularly being made in terms of efficiency, these breakthroughs come from controlled laboratory environments. To develop the next generation of heat-resilient perovskite hardware and to bring tandem PVs to the mainstream, researchers require consistent, repeatable conditions that mimic in situ use. Outdoor conditions are far too unpredictable for accurate R&D; therefore, scientists must replicate outdoor conditions via several well-structured laboratory protocols.
Image: Ossila.
Researchers can then use continuous thermal logging to track real-time voltage drops as temperatures rise over time. This is key when testing cell efficiency in both encapsulated perovskites and in tandem solar cells.
To test long-term durability, researchers can also perform lifetime testing. By employing accelerated degradation techniques, researchers can use tunable LED systems to simulate varying intensities of sunlight and mimic years of intense heatwaves. This allows researchers in any lab in the world to perform repeatable, consistent, and controlled device and material testing regardless of the climate.
Standard reliability protocols such as light-induced degradation or damp heat testing require cells to be exposed to continuous illumination for potentially thousands of hours. Tying up a single calibrated solar simulator in a shared lab to test one batch of cells at a time is both financially and logistically impractical.
Finding the durability of different materials under extreme solar spectra is a key stage of device testing and utilising multiple budget friendly, LED-powered solar simulators running parallel allows labs to scale up their research. Thus, leading to quicker and more accurate prototyping ensuring future developments can survive an increasingly hot climate.
There is no doubt that as temperatures continue to rise, the demand for renewable energy solutions will also increase. By utilising low-cost, versatile tools to replicate the exact solar spectrum, material scientists can push the boundaries of energy efficiency and device stability, ultimately reframing the narrative for the future of solar power. Instead of “how much solar can we build?” researchers are asking (and beginning to answer), “how can we make solar more climate-resistant?”
Read more about:
Stephen Gibbs
scientific content writer, Ossila
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