Some argue advances in perovskite solar cells mean we are on the brink of the next solar energy revolution. But it all depends on how they hold up in the real world.

Inside a lab on the outskirts of Oxford, UK, sample solar photovoltaic (PV) cells are stacked up waiting to be put through various tests. One researcher uses an electron microscope to scan and analyse the cells for impurities that could impact efficiency. Another measures cells' response to changes in the light spectrum.

The lab is run by Oxford PV, a spin-off from Oxford University, one of several start-ups around the world developing what some argue is the game-changing next generation of solar power: tandem perovskite solar cells.

The technology combines silicon, the material currently used in solar photovoltaics (PV) in panels across the world, with perovskite materials to massively increase the efficiency of solar panels' conversion of sunlight to electricity.

Perovskite is a mineral first discovered in the Ural Mountains in Eurasia in 1839. But the name today refers to various materials made synthetically with crystal structures that mirror that of the mineral. It can be manufactured from materials such as bromine, chlorine, lead and tin, which are all readily available today.

According to proponents of this "wonder material", perovskite panels promise to cheaply boost the energy generated by solar farms and rooftops, and could work far better than silicon panels on satellites and electric cars.

But critics of the technology worry that perovskite's greater susceptibility to moisture and heat will mean faster degradation. They are also concerned about perovskites generally containing lead, a toxic substance which can have health and environmental impacts.

Many of the start-ups and researchers working to overcome these hurdles believe that tandem panels are now ready to go mainstream. But despite the efficiency records piling out from labs, it is yet to be proven they will achieve tangible results in the real world.

Solar power now accounts for almost 7% of global electricity generation and is rising fast: it grew by 29% in 2024. It has also become the second-cheapest new source of electricity globally, including in the US (only onshore wind is cheaper). A 2023 analysis found the trajectory of solar technology may have already reached a tipping point towards dominating global electricity markets, even without further climate policies.

Conventional silicon panels dominate today's solar PV market, but their efficiency (a measure of the amount of sunlight converted to energy) has a relatively low upper limit. Efficiency is key for renewables, since expanding growth at the scale needed for global decarbonisation relies on producing the highest level of energy for the lowest possible cost.

The main advantage of perovskites over silicon is that they can convert more of the light spectrum into energy, due to a combination of factors including high mobility of electrons inside the cells.

Perovskite cells can be used by themselves in some applications. They are ultra-thin, meaning they can be sprayed onto surfaces, such as windows, with a number of companies currently piloting this technology. But using perovskites in tandem with silicon gives the benefits of both silicon and perovskites in terms of absorbing the Sun's energy. Silicon-only cells typically have an efficiency of 21-23% and though improvements are possible, the theoretical maximum is around 33%. In perovskite tandem solar cells the theoretical maximum efficiency increases to more than 47%.

Oxford PV says the ability of........

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