Today they are everywhere, from the roofs of our homes to large installations, from the space station to our smartwatches. But let’s go back almost 200 years and trace the history of photovoltaics: a key technology for sustainability

Year 1839; in a small Parisian laboratory, Edmond Becquerel – a 19-year-old boy – is tinkering in the workshop of his father Antoine, curator of the National Museum of Natural History. Edmond leans over a rudimentary apparatus, consisting of two electrodes immersed in a conductive solution. At that moment, the clouds clear and sunlight enters through the window, hitting the very device. Becquerel observes an unusual phenomenon: an electric current is spontaneously generated. That ray of sunlight, combined with the observational spirit of a very young scientist, triggers a revolution that, over a century later, will lead to the creation of photovoltaic panels, capable of converting sunlight into electrical energy. The young Becquerel certainly had no idea that his experiment, considered a scientific curiosity at the time, would become the basis for one of the most promising energy technologies of the 21st century.

Italy at the dawn of the photoelectric effect

In 1859 we find Antonio Pacinotti: he is famous for inventing the dynamo at the age of just 24. This is not only capable of converting mechanical energy into electricity, but, when run in reverse, converts electricity into mechanical work. In one fell swoop, the Pisan scientist laid the foundations for understanding the mechanisms of both the production and use of electricity, from wind turbines to nuclear reactors, from fans to electric cars. But it doesn’t end there: in 1863 we owe Pacinotti the observation that the electric current that forms between two plates of the same metal, one kept in the dark and one exposed to light of different wavelengths, is greater with blue radiation and less with red radiation.

His pupil, the Bolognese Augusto Righi, continued the path traced by his master and came to coin the term ‘photoelectric effect’.

Righi realises that light is not only a form of energy but can also release electrons from a material, an idea that will revolutionise modern physics. Righi goes one step further: he develops an oscillator that generates electromagnetic waves at very high frequencies, paving the way for future radio technology.

The first prototypes, thanks to selenium

The next stop on our journey is 1876, when William Grylls Adams and Richard Evans Day demonstrate that selenium generates electricity when exposed to light. This is a significant step forward, even though the amount of energy produced is modest. However, the discovery confirms that light can be converted into electricity, a concept that will become central in the future development of solar energy.

From theories to first applications

In Germany, Werner von Siemens, a well-known entrepreneur and scientist, also took an interest in solar energy. In 1881, he published an article in which he described the potential of the photovoltaic effect to generate electricity. Although his work remains mainly theoretical, Siemens clearly sees the future: the direct conversion of sunlight into electricity could revolutionise the world of energy. It is one of those moments when you can almost feel the air saturated with … electricity!

In 1883, US inventor Charles Fritts built the first photovoltaic cell. He uses a thin layer of selenium, coated with gold foil, to create a cell that converts about 1 per cent of sunlight into electricity. Today, this efficiency makes one smile, but at the time it was a stroke of genius. Fritts imagined a future in which house roofs would be covered with solar panels, a vision that anticipated the widespread adoption of solar energy by more than a century. Too bad that at the time, selenium was expensive and inefficient, making solar panels more of a dream than a commercial reality. Fritts didn’t give up and asked Siemens for help, which confirmed the validity of the experiment but failed to theoretically explain its effect, or to give Fritts’ prototype a commercial boost. Well, progress is not just a chain of successes, is it?

Einstein and the photoelectric effect

At the beginning of the 20th century, solar energy received a decisive boost thanks to two giants of physics: James Clerk Maxwell and Albert Einstein. Maxwell, with his electromagnetic theory, provided a fundamental explanation of the behaviour of light and electromagnetic waves. Then comes Einstein, who in 1905 publishes a paper describing the photoelectric effect, explaining how light can release electrons from a material, generating an electric current. Einstein did not directly construct photovoltaic cells, but laid the theoretical foundation for everything that would come later.

It was for this work – and not for the Theory of Relativity, which was considered too revolutionary even by the Swedish Academy – that Einstein received the 1921 Nobel Prize in Physics.

Silicon arrives with Pearson, Chapin and Fuller

In 1954, three Bell Laboratories scientists – Daryl Chapin, Calvin Fuller and Gerald Pearson – created the first silicon solar cell. This cell had an efficiency of 6%, a significant improvement over Fritts’ cell, and could be used to power small electronic devices. If Fritts had imagined the future, Chapin, Fuller and Pearson bring it one step closer to reality.

Bell Labs demonstrates the new technology by connecting a small solar cell to a rotating toy, powered solely by sunlight. The prototype is simple, but shows the world that solar energy is not just a scientific curiosity, but a reality that can have real applications. Basically, it is as if they had turned on a small light bulb – only that light bulb would one day illuminate entire cities.

Solar panels in space

In the 1960s, photovoltaic technology took a leap forward thanks to the space race. Satellites required a reliable energy source; and silicon solar panels proved ideal. The first satellite to use solar power is the Vanguard 1, launched in 1958: it uses a 1 Watt solar panel to power the on-board radio. Since then, almost all subsequent satellites have adopted solar panels and solar energy has become an essential element in space missions. Often a critical element, such as the failed deployment of the Skylab solar panels, which first crippled and then forced the Americans to abandon the project.

In a way, one could say that solar energy ‘takes flight’ – literally – and becomes one of the key technologies of the space age. Today, the International Space Station is powered by 262,400 solar cells covering an area equal to half a football field and producing up to 120 kW of electricity. The problem for the ISS is not the clouds but… the Earth, which shadows it for half of its orbit.

Photovoltaic panel generations

Research continues, and photovoltaic panel technology evolves through several generations:

First generation (crystalline silicon panels): These are the first commercial photovoltaic panels, based on crystalline silicon, first amorphous, then polycrystalline, and finally monocrystalline. They are efficient, durable and relatively easy to produce, although initially expensive.

Second generation (thin films): In the 1980s and 1990s, thin-film panels emerged, using materials such as cadmium telluride (CdTe), copper indium gallium diselenide (CIGS) or purely organic substances (OPVs). They are cheaper to produce and can be applied on flexible surfaces, but tend to be less efficient than crystalline silicon panels.

Third generation (perovskite cells and emerging technologies): More recently, research has focused on materials such as perovskites, which promise to further increase efficiency while reducing costs. Perovskite cells, still under development, could revolutionise the solar market.

Fourth generation (hybrid technologies): We are witnessing the emergence of hybrid technologies that combine different materials and production methods to create even more efficient and versatile solar panels. The goal is to improve conversion efficiency and make solar energy accessible on a large scale.

Italy and the first photovoltaic power plant

As solar energy begins to cover roofs all over the world, Italy too plays its part. In 1981, the first Italian photovoltaic plant was inaugurated in Passo della Mandriola, in the province of Rimini. This pilot plant, built by ENEL, has a capacity of 3 kW and represents an important step forward for solar energy in the country. Since then, Italy – with ups and downs as with every process in our country – has continued to invest in photovoltaics, becoming one of Europe’s leaders in solar energy production.

The continuing evolution of photovoltaics: a bright future

Today, photovoltaic panels are a mature and evolving technology. Production costs have fallen dramatically, making solar energy one of the cheapest energy sources in the world. According to the International Energy Agency, solar energy is the leading source of renewable energy, with more than 1,200 GW of installed capacity globally by the end of 2023. Forecasts indicate that by 2030, global solar capacity could exceed 3,300 GW, cementing its position as a pillar of the energy transition.

The collaboration of generations of scientists

The history of photovoltaic panels is an extraordinary example of how technological progress is never the result of a single individual, but of continuous teamwork across generations.

From Becquerel to Chapin, from Einstein to Fuller, every scientist has contributed a small part to building a technology that is now essential for a sustainable future.

And while we enjoy some sunshine, we know that every ray of light captured by solar panels is not only a step towards energy independence, but also a tribute to all those scientists thanks to whom we can now tackle the global challenges of climate change and build a world where clean energy is accessible to all.