To manufacture solar panels, 1 ton of purified silicon requires 2,000 tons of silica sand. Using the Czochralski method, silicon wafers are cut to 180 micrometers. Advanced treatments like anti-reflective coatings reduce sunlight loss to below 5%, boosting efficiency to 22-26%.
Raw Materials
The foundation of a solar panel starts with silicon, the primary material used in photovoltaic (PV) cells. Silicon is extracted from silica sand, a material that makes up some 26% of the Earth's crust. Mining and refining silica into metallurgical-grade silicon is the beginning of the process, with further purification into solar-grade polysilicon. It needs about 2,000 tons of raw silica sand to prepare 1 ton of the highly purified silicon. It is purified through a high-temperature Siemens process whereby impurities are removed until the silicon achieves a purity of 99.9999% (6N purity).
The primary choice is polysilicon, dominating 95% of the solar panel market due to cost-effectiveness, while monocrystalline silicon provides superior performance, having efficiency about 2-4% higher. Additional materials to protect solar panels include tempered glass making up 70% of the weight of the panel, aluminum frames weighing about 15 kgs, and encapsulants such as ethylene-vinyl acetate (EVA).
Silicon Processing
The process of transforming raw silicon into usable PV wafers involves the first step of melting silicon at temperatures higher than 1,450掳 C. To obtain monocrystalline ingots, manufacturers apply the so-called Czochralski method. One ingot can weigh as much as 200 kilograms and yield up to 1,000 wafers, each around 180-200 micrometers thick. All this provides identical crystal structures, which mean higher efficiency rates.
Conversely, polycrystalline silicon is produced through melting fragmented silicon and then letting it cool into multi-crystal structures. This method is less energy-intensive, hence cheaper, but cuts down on efficiency because the grain boundaries impede the flow of electrons. Normally, polycrystalline panels achieve efficiency rates of 15-18% compared to 20-22% for its monocrystalline counterpart.
Wafer Cutting and Polishing
The ingots are subsequently transformed into thin wafers by diamond wire saws. One ingot can yield as many as 200,000 wafers. Special machinery minimizes the amount of material lost by reducing kerf loss below 50 micrometers per cut. Chemical etching will then be used to eliminate any surface damage, while polishing will be done to achieve uniformity among the wafers.
High-precision polishing techniques improve light absorption in these smooth surfaces that become vital for efficiency higher than 20%. Some leading manufacturers use techniques of advanced surface passivation such as Tongwei and JinkoSolar that give quality wafers for improved efficiency.
Cell Formation
These wafers are then subjected to a series of high-tech processes to produce photovoltaic cells. The first step in this process is the doping of silicon with phosphorus (N-type) and boron (P-type) to create a PN junction, the heart of solar energy conversion.
Anti-Reflective Coating
Silicon naturally reflects up to 30% of sunlight, so an anti-reflective coating (ARC) is applied to minimize losses. This coating reduces reflection to below 5%, enhancing light absorption and overall efficiency. For instance, cutting-edge black silicon treatments have improved light absorption rates by an additional 1-2%.
Metallization and Contact Printing
Thin conductive lines on the surface of wafers are printed by a method called screen-printing technology with silver paste. One panel needs approximately 5-6 grams of silver to act like electrical pathways for the generated current. The multi-busbar technology is one such development that reduces resistance and hence increases efficiency by 3-5%.
State-of-the-art HJT and TOPCon (Tunnel Oxide Passivated Contact) cells provide a conversion efficiency of as much as 26%, an example being Longi Solar's latest modules. These technologies combine high light absorption with reduced electron recombination losses.
Panel Assembly
In the assembly section, individual cells are interlinked with each other to make solar modules. Standard panels contain 60, 72, or 144 cells, while commercial use requires larger dimensions. The output power has also reached up to 450-600 watts for the high-efficiency panels.
Encapsulation
Solar cells are sandwiched between protective layers: EVA encapsulants, tempered glass, and a polymer backsheet. EVA encapsulation ensures weather resistance and structural durability, while the tempered glass provides mechanical protection and transparency for light penetration. Lamination of the panel involves subjecting it to temperatures of 150掳C and vacuum pressure at 1,000 millibars.
To further improve the performance, some manufacturers also use POE (polyolefin elastomer) as encapsulants that offer better UV radiation and ingress of moistures, resulting in 5-10 years increased panel life.
#### Installation of the Frame and Junction Box
The aluminum frame provides mechanical strength to the module and prevents warping or damage during installation. A junction box is attached to the back, housing bypass diodes to minimize energy losses from shading. More advanced modules are also equipped with smart bypass technology, which reduces efficiency losses due to partial shading.
Quality Testing
Quality control is very tight in order to make solar panels reliable and long-lasting. Thermal cycling tests expose panels to extreme temperature variations of -40掳C to 85掳C for up to 1,000 cycles, emulating real-life conditions over tens of years.
Hail and Impact Tests
Panels undergo hail tests, with ice balls 25-45 mm in diameter striking the surface at 100 km/h. This ensures that tempered glass will not crack due to violent weather conditions.
Electroluminescence (EL) Testing
Electroluminescence Testing EL imaging detects microcracks and internal defects that cannot be seen with the naked human eye. A single crack can reduce efficiency by as much as 5-10%. Automated EL testing ensures that no defective panels leave the factory.
Flash testing determines the output performance of the panels under STC. A 400-watt-rated panel should be able to perform at a minimum of 95% of its rated capacity during its first year.
Encapsulation Process
The encapsulation process protects the internal solar cells from moisture, UV degradation, and mechanical stresses. EVA sheets are laminated around the cells under controlled temperature and pressure conditions.
Advanced materials include fluoropolymer backsheets and POE encapsulants, which have better resistance to hydrolysis and UV exposure, extending the module's life to 30-40 years. The vacuum lamination process ensures that there are no air pockets, which means delamination-one of the major reasons for efficiency loss-cannot take place.
Final Inspection
Final inspection includes a series of tests such as visual inspection, EL imaging, and outdoor performance validation. Microcracks or soldering defects can reduce panel lifespan by as much as 5-7 years if left unchecked.
Real-world simulations will validate output consistency under different levels of irradiance. A high-efficiency 400-watt panel can produce around 1.8 to 2.2 kWh/day, enough to keep all your essential household appliances running. Premium panels come with performance warranties, ensuring at least 90% output for 25 years.
Other leading manufacturers, such as Trina Solar and JA Solar, go further with their stress tests, including checks against PID (Potential Induced Degradation), which ensures very minimal degradation in high-voltage conditions.
