When Charles Fritts built the solid photovoltaic cell, he did not imagine the scope of that small surface made of selenium with a layer of gold. Credit: Smithsonian.

  • Innovation


Solar energy is the second fastest growing renewable energy in the world, according to the International Energy Agency. An industry that is key to providing electricity to 840 million people today. But this dream of guaranteeing universal access to electricity would not have been possible without Charles Fritts, author of the first solid solar cell, the forerunner of today's solar panels.


Charles Fritts' ingenious innovation was the first device to generate electricity by harnessing the power of the Sun, which produces the equivalent of four billion 100-watt light bulbs every second. This energy potential of the Sun had not gone unnoticed throughout history, as the first written records on the use of solar energy date back to the Romans and Greeks, two civilizations that already used it to light fires using mirrors or "burning" lenses. However, the definitive door to the development of solar energy was opened much later by French physicist Alexandre Edmond Becquerel, who discovered the photovoltaic effect in 1838.

Nowadays we understand how this effect works. We know that when light strikes a semiconductor material and increases the mobility of its electrons, the voltage moves them in a specific direction and an electric current is generated. In 1873, English electrical engineer Willoughby Smith observed photoconductivity in practice in selenium (a semiconductor) while experimenting on materials for underwater telegraph cables. This discovery caught the attention of natural philosophy professor William Grylls Adams and his student, Richard Evans Day, who years later followed in the footsteps of the man considered to be father of photovoltaics. Together they presented the Royal Society with an article entitled The Action of Light on Selenium (1877) and succeeded in building a selenium solar cell in a glass tube. However, it was not until 1883 that New York inventor Charles Fritts (1850-1903) managed to produce the photovoltaic effect with a device that became the origin of today's solar panels. His feat was published in the 1883 paper: “On a New Form of Selenium Photocell” in the American Journal of Science.

Fritts' true solar cell projection didn't come until 70 years later, when Bell Labs got the marketable and functional photovoltaic cell. Credit: Bell.

A first prototype that impressed the founder of Siemens

Fritts lived and worked in a building in New York, on whose roof he gave free rein to his ingenuity. His inventions ranged from clockwork mechanisms to curtain accessories to mechanical devices to optimize the coupling of train cars. This is where the device that would make him go down in history was born: a glass box containing a selenium sheet housed between two metallic layers (an upper one of thin, semi-transparent gold-leaf, and a lower one of a metallic substrate of brass). When light shone into the box, electrons moved through the selenium and a current was produced which was then sent out through a wire at one end of the box: "a continuous, constant current of considerable force," according to Charles Fritts himself. Excited, he sent one of his prototypes to German engineer Werner von Siemens, who was so impressed by the generation of electricity from sunlight that he presented Fritts' invention to the Royal Academy of Prussia and stated that the American’s modules "presented to us, for the first time, the direct conversion of the energy of light into electrical energy."

At that time, the commercial electricity revolution was underway in New York, and Thomas Edison commissioned the first coal-fired power plant in history (1882). Charles Fritts was optimistic about the potential of his invention and thought it could compete with Edison's power plant. But the truth is that Fritts' cell only made use of about 1% of the sunlight and did not have enough capacity to make the jump to the consumer market. The New York inventor likely had no idea how long it would take industry to optimize his invention: 70 years would pass until Bell Labs produced modern solar technology in the mid-20th century.

Solar energy is one of the renewables with the highest growth prospects in the coming years. Credit: Science in HD.

From powering space satellites to a million dollar industry

However, Fritts' selenium cells did find other applications, as they were used as light sensors to control the exposure time of cameras and even eventually served to power space satellites of all kinds, a market for which the cost of selenium was no obstacle.

These days, Fritts' dream has become a multi-billion-dollar industry that, according to figures from the World Bank, is key to providing power to 840 million people currently without access to electricity. Technological advances have also made it possible to achieve an efficiency of up to 24% in some solar cell models, making this energy source not only an essential technology for achieving sustainability, but also the great promise for guaranteeing universal access to electrical energy, almost 150 years after the first light bulb was switched on.

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Tungsteno is a journalism laboratory to scan the essence of innovation. Devised by Materia Publicaciones Científicas for Sacyr’s blog.

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