It is widely reported that humans have been harnessing the sun's power as far back as the 7th century B.C. It has had many applications over this time. From concentrating the sun's rays through magnifying glasses to create fire, warming the water in Roman bathhouses and aiding food cooking using solar collectors in the 18th century.
The history of solar is vast. So, for the purpose of this article, we will only report on the key events that contributed to the development of the modern-day solar PV panels used to generate electricity.
The photovoltaic effect was discovered by the 19-year-old physicist Alexandre Becquerel. While experimenting with metal electrodes and some electrolytes, he noticed an increase in conductivity when it was illuminated with light.
This is the basis on which all solar cells work. When sunlight hits a semiconducting material like a solar cell, there is a change in the voltage and current. You can find out more about how solar cells work here.
Willoughby Smith was an electrical engineer from England. He worked for the Gutta Percha Company, which developed the first rubber insulated cable.
In 1866, Willoughby developed a test that allowed him to check cables continuously while being laid underwater. He needed a semiconducting material for this test, so he used selenium. But the results he got were inconsistent and not what he was expecting.
Later it was discovered that when the selenium rods were illuminated with light, there was a significant rise in their conductivity.
The observation of photo-conductivity in selenium led to more investigations by other scientists.
One such scientist was William Grylls Adams, a professor in London. He and his student Richard Evans Day also witnessed the photovoltaic effect when they exposed selenium to light and produced an electrical current.
This proved that solid materials could change sunlight into electricity without heat or moving parts. This was when the idea for producing solar cells was born.
An American inventor named Charles Fritts created the first commercial solar cells from selenium. However, these solar cells were very inefficient. Only 1% of the light that hit the cell was converted into electricity.
Due to this, solar power was not a viable replacement for power plants. However, Fritts predicted that solar cells may compete with coal-fired power plants one day.
It was all well and good to observe the photovoltaic effect. However, nobody could really explain what was going on inside the materials. This was until Albert Einstein wrote his famous paper in 1905 on the photoelectric effect.
He explained that light contained little packets of energy called light quanta, and how materials could absorb these light quanta to produce electricity. These light quanta are now known as photons.
In 1914, Goldman and Brodsky reported the correlation of the photoelectric effect with the existence of a barrier to current flow at a semiconductor-metal interface. This knowledge helped to provide critical insights necessary for building practical photovoltaic devices.
A scientist named Robert Milikan set out to prove Albert Einstein's theory of the photoelectric effect wrong. So he performed an experiment in a vacuum to show that something else in the environment (not light) caused the electrons to absorb energy and be emitted from a material. Unfortunately (or fortunately, depending on your perspective), he proved Einstein's theory correct.
Jan Czochralski was a Polish chemist who invented the' Czochralski' method of growing single crystals of metals, semiconductors, salts and gemstones.
He discovered this by accident when he mistakenly placed his pen into a pot of molten tin instead of his ink well. When he drew out his pen from the pot, he was left with a thin filament that, upon further inspection, turned out to be a single crystal.
Based on this, he developed his method of making single crystals which is still used today. This method contributed greatly to making silicon ingots used to manufacture modern solar cells. You can read more about how solar cells are made here.
Albert Einstein's work was recognised in 1921 when he was awarded the Noble Prize for Physics for his contribution to Theoretical Physics and, in particular, for his explanation of the photoelectric effect.
Russell Ohl was an American engineer. His primary area of research was into the behaviour of certain types of crystals. In 1939, Ohl discovered the mechanism by which the p-n junction worked. See more on the p-n junction in our article on how solar panels work here.
Until then, nobody understood the effect of impurities in the photovoltaic cell. He discovered that the barrier between the different purities made the solar cells work.
Later, Ohl was able to make usable and predictable semiconductor materials by super-purifying germanium. In 1941 he used what he had learned to design and patent the modern solar cell.
One of the most significant barriers to taking solar technology to the masses was its efficiency. Up to 1954, solar cells could not produce enough electricity to power electrical devices.
However, in 1954, Bell Labs scientists Daryl Chapin, Calvin Fuller, and Gerald Pearson constructed a solar cell with 6% efficiency, providing enough electricity to run electrical devices.
According to the New York Times, this achievement marked 'the beginning of a new era, leading eventually to the realisation of one of mankind's most cherished dreams—the harnessing of the almost limitless energy of the sun for the uses of civilisation.' Judging by the way things are going, they may have been right!
AT&T owned Bell Labs and Western Electric. In 1955 Western Electric began licensing solar cell technologies commercially. It is reported the technology had an output efficiency of around 2%.
In 1957, Hoffman Electronics were able to introduce cells with increased efficiency, at 8%.
In 1957 an American/Egyptian engineer named Carl Frosch developed a process called surface passivation which drastically improved the lifetime and efficiency of solar cells.
This process involves coating a very thin layer of material onto the solar cell, which creates a shield around it. He discovered that coating the solar cell in a very thin layer of silicon dioxide helped to preserve the electrical characteristic at the p-n junction and stop them from deteriorating into the surrounding gaseous environment.
Silicon-dioxide passivation is still used in the production of solar cells today.
Solar cell technology was well on its way in the late 1950s. The biggest challenge at this stage was still achieving greater efficiencies. In 1958, Hoffman Electronics improved its cell efficiency by 1%, to 9%.
In 1959, Hoffman Electronics created a 10% efficient commercial solar cell. They also introduced a grid contact which reduced the cell's resistance.
In the late 1950s, Sharp Corporation invested a lot of effort into solar-powered research. In 1963, they produced a viable photovoltaic module of silicon solar cells that they then mass-produced.
The Centre for Photovoltaic Engineering at the University of New South Wales created silicon solar cells with 20% efficient silicon cells. This 20% efficiency solar cell was patented in 1992.
By the late '90s, solar had come a long way. At this stage, worldwide solar PV installations surpassed 1 GW.
Since the development of the modern-day solar cell in 1950s, they have been used extensively across many industries with many applications.
For example, solar technology has played a significant role in the space industry, where solar has been used to power satellites. It became the accepted energy source for space application, and it remains so today. Solar has also been used to power simple devices such as the calculators we have all used in school. The technology has also been incorporated into the roof of cars, providing a fuel efficiency bump of up to 8% for those who average around 10,000 miles per year.
Today, as we are confronted by the global environmental crisis, solar power is increasingly considered a key "clean energy" source for the 21st century.
Here, we break down the science behind them and explain how solar panels actually generate energy. Read more...
A look behind the scenes at how solar panels are made. From sand to high-tech on your roof. Read more...
A no-nonsense guide to understanding the jargon and slang often used in the solar industry. Read more...
A look at the 10 biggest misconceptions regarding solar power and the truth behind them. Read more...
Detailing the effect shading has on your panels, what causes it and the best ways of avoiding it. Read more...
The difference between, and the pros and cons, of solar thermal systems and solar PV systems. Read more...