Unlocking The Sun: How Solar Panels Really Work

India.com

11-07-2025

To make these solar panels, Indian companies need PV cells—which are the small parts that convert sunlight into electricity. Since India doesn't yet make enough of these cells on its own, it is importing more from China to support its growing solar panel production.
In simple words, as India builds more solar panels at home, it is also buying more parts from China to keep up with the demand.
Two Simple Ways the World Generates Electricity: Moving Machines and Sunlight Power
There are basically two main ways to produce electricity.
The first method was discovered by Michael Faraday in 1821. It works by spinning a coil of wire near a magnet or spinning a magnet near a coil of wire. This movement creates electricity. This idea became useful by 1890 and is still the main way we produce electricity today. It is used in power plants, wind turbines, and hydroelectric dams, where machines spin to generate power.
The second method uses solar photovoltaic (PV) cells, which are made from materials like silicon, found in sand. This method was first noticed by Alexander Becquerel in 1839, when he saw that sunlight can directly produce electricity. This is called the photovoltaic effect and is used in solar panels.
So, one method makes electricity by spinning parts inside machines, and the other makes electricity directly from sunlight using special materials.
Breakthroughs That Made Solar Power Possible
The first useful solar cell was made in 1954 by scientists at Bell Labs—Chapin, Fuller, and Pearson. They used a special type of silicon called doped silicon, which helps produce electricity from sunlight more efficiently.
This big step was possible because of two important discoveries:
Albert Einstein explained how light can produce electricity—called the photoelectric effect. He won the Nobel Prize for this work. Jan Czochralski, a scientist from Poland, found a way to make single-crystal silicon, which is now the main material used in most solar cells.
These two breakthroughs helped make modern solar panels possible.
Simple Solar Tech Beyond Power Grids
Unlike solar panels (PVs) that send electricity into the main power grid and are taxed and regulated, other solar technologies like solar water heating, space heating, and solar cooling usually work on their own. They don't connect to the electricity grid.
For example, solar cooling uses a method called absorption refrigeration, which can cool indoor spaces to around 19°C even when it's 40°C outside.
A solar cooler uses energy from the sun to run a cooling system—just like how a fridge or air conditioner works, but without using regular electricity.
These technologies are like the solar panels used in faraway places, where there is no power supply. In such areas, solar panels are mainly used to charge batteries and give basic lighting.
Focusing Sunlight for Everyday Use
Different parts of the world receive different amounts of sunlight, a measure called solar insolation. While the sun gives us a huge amount of energy, it is spread out thinly over large areas. This means that at any one place, the sunlight is not very strong, making it hard to use directly for things like generating electricity or running machines.
To solve this problem, we use special tools and technologies to collect and focus the sunlight in one spot. These include parabolic troughs, Fresnel lenses, and other solar concentrators. Once the sunlight is focused, it becomes strong enough to be used for heating, cooking, removing salt from seawater (desalination), and producing electricity.
In simple terms, these tools help us make the most of the sun's energy by turning weak sunlight into powerful heat or power.
How Silicon Behaves in Solar Cells
PV (photovoltaic) cells are made from semiconductors like silicon. A semiconductor is a special material that conducts electricity better than insulators (like plastic) but not as well as metals (like copper). Silicon is the most common semiconductor used in solar cells.
On its own, silicon doesn't conduct electricity very well. But when it is heated or exposed to sunlight, or when it is treated with small amounts of other elements (a process called doping), it starts conducting electricity more effectively. This makes silicon very useful for making solar panels and electronic devices.
Copper, which is a good conductor of electricity, becomes less efficient when it gets hot—its resistance increases, which slows down the flow of current. That's why it is called an Ohmic conductor.
But silicon works in the opposite way. At room temperature, it does not conduct electricity well. But as the temperature goes up, silicon starts conducting better. This special behaviour makes it a non-Ohmic material.
This unique property of silicon is one reason why it is used in solar cells to convert sunlight into electricity.
How Electrons Flow to Make Electricity
According to quantum theory—which explains how very tiny particles like electrons behave—electricity flows only when electrons have enough energy to move freely.
In simple terms, electrons can only sit at fixed energy levels, just like people can only stand on the steps of a staircase—not in between. To help carry electricity, electrons need to reach a higher energy level called the conduction band, where they can move around freely, like water flowing in a river.
When electrons are at a lower energy level, called the valence band, they stay close to their atoms and can't move around, so they don't help in producing electricity.
To jump from the valence band to the conduction band, an electron needs extra energy. This energy can come from heat—when atoms vibrate more due to high temperature—or from light, like sunlight hitting a solar cell.
Once the electron absorbs this energy, it makes the jump and starts flowing, helping generate electric current. If it doesn't get enough energy, it stays in place and no electricity is produced.
How Light Helps Electrons Move
Light is a form of energy, and it can act like a wave or like tiny particles called photons, depending on how we observe it.
Each photon carries a small amount of energy. When sunlight hits a solar panel, these photons strike the electrons in the valence band (the lower energy level).
If a photon has enough energy, it can give that energy to an electron, helping it jump to the conduction band, where the electron can move freely and create electricity.
In simple words, light gives electrons the push they need to start flowing and produce power.
When Light Has Just the Right Energy
For an electron to jump from the valence band to the conduction band, the photon (light particle) must have just the right amount of energy. This rule was first explained by Albert Einstein in his photoelectric effect theory.
The needed energy is called the band gap—it is the energy difference between the two bands, and it is measured in units called electron volts.
If the photon's energy is less than the band gap, the electron won't move. If the photon has more energy than needed, the extra energy is wasted as heat, and this can even cause some electrons to be lost.
So, for solar panels to work well, the light must match the material's band gap, giving just enough energy to move the electrons and make electricity without much waste.
Why Some Sunlight Can't Be Used
To produce electricity from sunlight, two conditions must be met:
The photon must have the right amount of energy (called the energy criterion). The movement of the electron must match certain patterns (called the symmetry criterion), though this is less important here.
Because of these rules, about 50% of sunlight that reaches Earth can't be used by regular solar cells made of crystalline silicon.
Around 20% of the sunlight has too little energy, so it can't move the electrons. About 30% has too much energy, and the extra energy turns into heat, which is wasted.
Some other materials—like gallium arsenide, cadmium telluride, and copper indium selenide—can absorb different parts of sunlight more effectively. But they are hard to find, tricky to handle, or harmful to the environment, which makes them difficult to use widely.
That's why crystalline silicon remains the most common material in solar panels, even though it doesn't use all the sunlight.
How Boron and Phosphorus Make Solar Cells Work
In silicon-based solar cells, small amounts of two elements—phosphorus and boron—are added to pure silicon to change how it behaves.
When phosphorus is added to silicon, it gives the silicon extra electrons. This side is called the n-type (negative) region. When boron is added, it creates 'holes'—which means there are fewer electrons. This side is called the p-type (positive) region.
Where the p-type and n-type silicon meet, a special area forms called a p-n junction. At this junction, an electric field is created—like a built-in push that wants to move electrons in one direction.
When sunlight hits the solar cell, it gives energy to the electrons. These electrons jump across the p-n junction and start flowing. This flow of electrons is what we call electricity—just like in a battery.
So, by carefully combining boron and phosphorus with silicon, scientists create a material that converts sunlight into electric power in a simple and clean way.
How Electricity Flows and Why Some Energy Is Lost
When we connect a wire or device (called a load) to a solar cell, the electrons start to flow from the negative side (with more electrons) to the positive side (with fewer electrons). This movement of electrons through the load completes the circuit and creates electricity we can use.
As long as sunlight is available, this flow of electricity can keep going without stopping.
But even from the 49.6% of sunlight that solar cells can use, some energy is still lost:
Solar panels get hot—they can become 30 to 40°C hotter than the air around them. This heat is released back into the air and causes about 7% energy loss.
Another 10% energy is lost due to a problem called the saturation effect. This happens because electrons and holes (positive charges) don't move at the same speed, which weakens the electric push (voltage) in the solar cell over time.
So, while solar cells are very useful, not all sunlight is turned into electricity, and some energy is always lost as heat or due to how charges move inside the cell.
Why Solar Cells Can't Use All Sunlight
Even in the best conditions, a single-junction silicon solar cell can only turn about 33.7% of sunlight into electricity. This limit is called the Shockley-Queisser limit, and it's based on how solar energy and materials work at the atomic level.
This means that, in theory, two-thirds of the sunlight's energy is always lost, no matter how good the solar cell is.
In real life, solar panels lose even more energy because of practical issues, such as:
Some parts of the panel get more sunlight than others (uneven lighting). Small differences in how each cell is made during production can lead to mismatched voltages across the panel.
All these factors together make sure that actual efficiency is always lower than the theoretical limit.
How Much Sunlight Solar Panels Really Use
In real-world use, solar panels lose more energy during other steps, like:
Changing the electricity from DC (direct current) to AC (alternating current) so it can be used in homes. Adjusting the panel to work at its best power point (MPP) throughout the day.
Because of these extra losses, the actual efficiency of solar panels is lower:
In the best lab conditions, silicon solar panels can reach about 25% efficiency. In the real world, even the best commercial panels usually reach only about 20% efficiency.
To understand how good this is—natural photosynthesis (how plants use sunlight to grow) only captures about 3% to 6% of sunlight. So, even with losses, solar panels are much better at using sunlight than plants.
Making Solar Cells from Shiny Silicon
Natural silicon is very shiny, so it reflects a lot of sunlight. To stop this and help the silicon absorb more sunlight, a special anti-reflection coating is added—usually made of tin oxide or silicon nitride. This coating also gives solar panels their blue color.
Unlike plants, which build their energy systems naturally and at normal temperatures, making solar panels takes a lot of energy.
The process starts by purifying silicon. Natural silicon is cleaned until it is 99% pure, using something called the Czochralski process. In this method, silicon is melted, and then slowly cooled and shaped into a single large crystal, called an ingot. These crystals are later cut and used to make solar cells.
So, while solar power is clean, making solar cells requires careful steps and energy.
Cutting and Cost-Saving in Solar Cell Making
After purifying silicon into large crystals (called ingots), these are sliced into thin wafers to make solar cells. But this slicing causes about 20% of the silicon to be lost as dust, which makes the process expensive.
To reduce this waste and cost, scientists have developed new methods, like ribbon technology, which makes thin silicon strips without cutting big crystals. This saves material and money.
Another cheaper option is using amorphous silicon, which doesn't have a clear crystal shape. Though it has natural defects, these can be fixed by adding a small amount of hydrogen. This helps improve its performance.
As Dr. Arunangshu Das from IIT's Centre for Atmospheric Sciences explains, these new techniques help lower the cost of making solar cells, making solar power more affordable.
New Types of Solar Cells for Better Efficiency
Some solar panels are now made using multijunction amorphous cells, which are designed to capture more parts of sunlight. These can reach a theoretical efficiency of up to 42%, though in real-life use, they usually reach around 24% efficiency.
According to Dr. Anurag Das, these advanced designs are helping to improve how much electricity we can get from sunlight.
Today's solar panel technologies are grouped into three generations:
First-generation: Uses thick silicon wafers, about 200 micrometers thick. These are the traditional and most common type.
Second-generation: Uses thin silicon layers, only 1 to 10 micrometers thick. These are cheaper to make and use less material.
Third-generation: Includes multijunction cells, tandem cells, and quantum dots. These new technologies can produce more electricity from each photon and, in some cases, even go beyond the normal efficiency limit (called the Shockley-Queisser limit).
These improvements are helping make solar energy more efficient and powerful, using the same sunlight more wisely.
Why Solar Power Is Getting Cheaper
The cost of solar electricity is falling fast. Back in 2010, it cost around $4 to $5 for every watt of DC power. By 2023, the cost dropped to about $2.80, and for large utility solar systems, it went down even further to $1.27 per watt. This drop matches the U.S. government's SunShot goal of bringing the cost to $1 per watt for full solar systems.
Let's look at where the money goes in a solar setup:
38% is spent on the solar panels (modules). 8% goes to power electronics, mostly the inverter that changes DC to AC. 22% covers wiring and mounting (how the panels are fixed in place). The remaining 33% is for hardware balance—this includes labour, permits, company overheads, and profits.
Now that single crystal solar cells are already close to their maximum power output, the best way to reduce costs further is by saving money in the hardware balance part—like making installations easier, faster, and cheaper.
What Affects Solar Panel Performance Over Time
Solar panels slowly lose efficiency over the years—about 0.5% per year. But most panels still work well for 20 to 25 years.
Many people think hot, sunny places like deserts and tropical regions are best for solar panels. While these areas get more sunlight, solar panels actually work better in cooler, clear-weather conditions. That's because heat reduces their efficiency.
This makes it harder for low- and middle-income countries, especially those in tropical or equatorial regions, to fully benefit from solar energy. They may face challenges like high temperatures, lack of infrastructure, or less efficient panel performance.
Also, air pollution can block sunlight and reduce the amount of energy produced by about 2 to 11%. On top of that, dust and dirt (called soiling) on the panels can cause another 3 to 4% loss in energy each year.
So, while solar power is a clean and powerful energy source, climate, pollution, and maintenance all affect how well it works in different places.
Challenges of Using Solar Panels in Cities
Cleaning solar panels regularly is important, but it can be risky and difficult. When the sun is shining, the panels are electrically active, which means touching them with water or tools can be dangerous. Also, cleaning them often uses a lot of water, which can be a problem in dry areas.
In crowded cities, solar panels can also trap heat, making the area around them hotter. This can lead to what is called the urban heat island effect, where cities become warmer than nearby rural areas.
Other solar technologies, like solar water heaters or solar cookers, can support solar panels, but they can't fully replace them.
Whether solar power alone can fully replace fossil fuels and help achieve a carbon-free future is still being studied and debated by scientists.
Why India Depends on China for PV Cells
India is growing fast in solar power, but it still depends heavily on China for solar photovoltaic (PV) cells. Here's why:
China Makes Them Cheaper
China has a well-established, large-scale manufacturing system for PV cells. It produces them in huge quantities, which makes the cost much lower than what Indian companies can offer right now.
Lack of Raw Material Processing in India
PV cells need high-purity silicon and other special materials. China controls most of the global supply chains for these materials and has better technology for purifying and processing them.
Advanced Technology and Machinery
Chinese factories use latest machines and production methods that make PV cells more efficient and cheaper. India is still building this kind of advanced manufacturing base.
Government Support in China
The Chinese government gives strong support through subsidies, cheap land, and loans, which helps their companies sell at lower prices globally. Indian manufacturers struggle to compete with these advantages.
Slow Growth of Local Industry
Although India has plans like PLI (Production Linked Incentive) schemes to boost local solar manufacturing, it will take time to build full supply chains and reduce import dependence.
In short, India depends on China for PV cells today because China is cheaper, faster, and better equipped. But India is working towards becoming self-reliant in solar manufacturing in the coming years.