How Solar Panels Work: Photovoltaic Cells Explained

Every solar panel is built from photovoltaic cells, thin slices of semiconductor that turn light into electricity with no moving parts, no fuel and no noise. Understanding how a PV cell works makes it easier to compare panels, read a datasheet and size a system. This guide walks through the photovoltaic effect step by step, the main cell types from monocrystalline to perovskite, current efficiency records and the components of a home solar system. For the bigger picture, see our renewable energy homepage and the solar energy guide.

What is a photovoltaic cell?

A photovoltaic (PV) cell, or solar cell, is a semiconductor device that converts sunlight directly into direct-current electricity through the photovoltaic effect. Most commercial cells are made of crystalline silicon about the thickness of a few sheets of paper.

The word “photovoltaic” joins “photo” (light) and “volt” (the unit of electrical potential). A single cell produces only a fraction of a volt, so manufacturers wire dozens of cells together into a module, or solar panel, and seal them behind tempered glass in an aluminum frame.

Key terms used in this guide:

• Semiconductor: a material, like silicon, whose ability to conduct electricity sits between a metal and an insulator and can be controlled by adding impurities.
• Doping: adding small amounts of other elements to silicon. Phosphorus adds spare electrons (n-type); boron creates “holes,” or missing electrons (p-type).
• P-n junction: the boundary where n-type and p-type silicon meet, which creates a built-in electric field.
• Band gap: the minimum energy a photon must carry to free an electron. Silicon’s band gap suits much of the sunlight spectrum.

How does a photovoltaic cell work?

A PV cell works by letting photons knock electrons loose in a semiconductor, then using the electric field at a p-n junction to push those electrons through an external circuit. The flow of electrons is the electric current.

The photovoltaic effect, step by step:

1. Light arrives. Sunlight, a stream of photons, passes through the glass and an anti-reflective coating that helps the cell absorb more light.
2. Photons are absorbed. A photon with energy above silicon’s band gap is absorbed by the silicon crystal.
3. An electron-hole pair forms. The absorbed energy frees an electron, leaving behind a positively charged hole.
4. The junction separates charges. The built-in electric field at the p-n junction sweeps electrons toward the n-type side and holes toward the p-type side, stopping them from simply recombining.
5. Contacts collect current. Thin metal fingers on the front and a contact on the back gather the electrons.
6. Current flows through a load. When the cell is connected in a circuit, electrons travel through wires, do work (such as powering a light) and return to fill holes on the other side.
7. Voltage builds up in series. Each cell gives a small voltage; wiring cells in series adds their voltages to a useful level for an inverter or charge controller.

The DOE summarizes it this way: energy from sunlight absorbed by PV cells creates electrical charges that move in response to an internal electrical field, causing electricity to flow.

Why cells cannot convert all sunlight

Photons with less energy than the band gap pass through without freeing electrons, and photons with much more energy waste the excess as heat. Some light also reflects off the surface, and some freed electrons recombine before they are collected. Together these losses set the Shockley-Queisser limit for a single-junction cell. Shockley and Queisser (1961) derived it from detailed balance and found a maximum near 30% for a 1.1 eV band gap under their idealized sun; recalculated for today’s standard solar spectrum, the commonly quoted peak is about 33.7%. Tandem and multi-junction cells beat that limit by stacking materials with different band gaps, each tuned to a different part of the spectrum.

What are the types of solar cells?

The main types of solar cells are monocrystalline silicon, polycrystalline silicon and thin-film, plus newer high-efficiency silicon designs (PERC, TOPCon, heterojunction, back-contact) and emerging perovskite and tandem cells. Monocrystalline silicon dominates today’s market.

Cell type	What it is	Strengths	Weaknesses
Monocrystalline silicon	Cut from a single silicon crystal; uniform dark look	Highest efficiency among mainstream panels	Energy-intensive crystal growth
Polycrystalline silicon	Cast from many silicon crystals; blue, speckled look	Historically cheaper	Lower efficiency; largely phased out of new installs
Thin-film (CdTe, CIGS, amorphous Si)	Very thin absorber layers deposited on glass or flexible substrates	Low material use, good in heat, flexible options	Generally lower efficiency than mono silicon; CdTe used mainly in utility projects
PERC	Monocrystalline cell with a passivated rear layer that reflects light back	Cheap upgrade over basic cells	Being overtaken by TOPCon
TOPCon	Tunnel-oxide passivated contact on n-type silicon	Higher efficiency than PERC on similar production lines	Slightly more complex process
Heterojunction (HJT)	Crystalline silicon sandwiched between thin amorphous silicon layers	High efficiency, good hot-weather performance	Higher material cost
Back-contact (IBC, HIBC)	All contacts moved to the rear, so no front shading	Record single-junction efficiency (27.81%, LONGi HIBC)	Complex to make
Perovskite	Low-cost crystal absorber that can be printed or coated	Tunable band gap, rapid lab progress	Long-term outdoor stability still being proven
Perovskite-silicon tandem	A perovskite cell stacked on a silicon cell	Breaks the single-junction limit (34.85% record, LONGi)	Not yet in mass production at scale

Mono vs poly: which should you buy?

Monocrystalline panels are the default choice for homes. They are more efficient, which means more watts from a limited roof, and price differences with polycrystalline have largely disappeared.

TOPCon vs HJT vs back-contact

These are all monocrystalline n-type technologies that cut electron losses at the cell’s surfaces and contacts. On a datasheet, they show up as higher module efficiency and often a lower temperature coefficient, meaning less power loss on hot days. Compare actual datasheet figures rather than the technology label.

How efficient are photovoltaic cells?

PV cell efficiency is the share of sunlight energy striking a cell that it converts into electricity. Lab records now reach 34.85% for flat-plate perovskite-silicon tandems and 47.6% for multi-junction cells under concentrated light, while commercial panels are well below lab cell records.

The standard reference for records is NREL’s Best Research-Cell Efficiency Chart, which plots the highest confirmed research-cell efficiencies for many PV technologies from 1976 to the present. Results are independently measured by test labs such as NREL, Fraunhofer ISE, AIST and JRC-ESTI, and the most recent record for each technology is flagged on the right edge of the chart. NREL, which now publishes as the National Laboratory of the Rockies (NLR), last updated the chart in August 2026.

Record	Efficiency	Who, when, certified by
Four-junction concentrator cell (665 suns)	47.6%	Fraunhofer ISE, 2022
Perovskite-silicon tandem (two-terminal)	34.85%	LONGi, April 2025, certified by NREL (pv magazine)
Previous perovskite-silicon tandem record	34.6%	LONGi, June 2024
Single-junction silicon (HIBC)	27.81%	LONGi, 2025, certified by ISFH
Single-junction theoretical limit	about 33.7%	Shockley-Queisser limit (1961 paper, modern spectrum)

Three things to keep in mind when reading efficiency numbers:

• Cell vs module. Records are for small research cells. The twice-yearly Solar cell efficiency tables (Green et al., 2026) list cell and module records separately, and module figures are consistently lower. A full commercial module has gaps between cells, frame area and wiring losses, so it is less efficient than its best cells.
• Concentrated vs one sun. The 47.6% record was measured under 665 times normal sunlight using lenses or mirrors; it does not apply to rooftop panels.
• Efficiency is not output. A more efficient panel makes more watts per square foot, but a cheaper, less efficient panel can still be the better buy if you have plenty of roof space.

What are the parts of a solar panel system?

A home solar system includes the panels, mounting racks, an inverter, wiring and disconnects, a production meter and often a battery. Off-grid systems add a charge controller and a larger battery bank.

Component	What it does
Solar panels (modules)	Convert sunlight into DC electricity
Racking and mounts	Hold panels at the right tilt and orientation on a roof or ground frame
String inverter	Converts DC from a whole string of panels into AC
Microinverters or power optimizers	Handle conversion or optimization panel by panel, reducing shading losses
Charge controller	Regulates battery charging in off-grid and DC-coupled systems
Battery	Stores surplus energy for night or outages
Disconnects and breakers	Safety shutoffs required by electrical codes
Net or bidirectional meter	Measures power imported from and exported to the grid
Monitoring	App or portal showing production and use

Battery pairing is rising fast. Berkeley Lab’s 2026 distributed solar data update shows 37% of new US residential solar systems were paired with batteries in 2025, up from 25% in 2024. For off-grid designs, use the solar charge controller calculator and read the off-grid solar system guide.

How do solar panels produce electricity for your home?

Solar panels produce DC electricity, an inverter converts it to AC, and your home uses that power first before sending any surplus to a battery or the grid. The process happens automatically whenever the sun is up.

1. Panels generate DC power from sunlight.
2. The inverter converts DC to 120/240-volt AC for household circuits.
3. Your home’s loads draw solar power first.
4. Surplus charges a battery, if installed.
5. Remaining surplus flows to the grid through the meter, credited under your utility’s tariff.
6. At night or on dull days, you draw from the battery or the grid.

Before a rooftop system goes in, check the solar panel installation permit rules, including the 33% roof rule for fire setbacks. Small kits that plug into an outlet are now legal in ten states; see our plug-in solar laws by state.

How much the system produces over a year depends on sunlight, panel orientation and losses. US utility-scale PV averaged a 24.0% capacity factor in 2025 (EIA), meaning it produced about a quarter of what it would at full power around the clock. Estimate your own array with the solar panel calculator and set the best tilt with the solar panel angle calculator. If kilowatt-hours are unfamiliar, read what is a kilowatt-hour.

What reduces solar panel performance?

Heat, shade, dirt, poor orientation and age all reduce how much electricity PV cells deliver. Most of these losses are predictable and can be minimized with good design.

• Temperature: cell voltage drops as cells heat up. The datasheet’s temperature coefficient shows how much power is lost per degree above 77°F (25°C).
• Shading: a shaded cell can limit current through the cells wired in series with it; bypass diodes, optimizers and microinverters limit the damage.
• Soiling: dust, pollen, snow and bird droppings block light.
• Orientation: panels facing away from the sun or at a poor tilt collect less energy.
• Degradation: cells slowly lose output over time, as stated in each manufacturer’s warranty.
• System losses: wiring resistance and inverter conversion take a few percent.

For a balanced look at the trade-offs of going solar, see solar energy pros and cons.

What are solar panels made of, and how are they made?

A typical solar panel is made of crystalline silicon cells with thin silver and copper contacts, sealed in a clear polymer encapsulant (usually EVA) between a tempered glass front and a plastic backsheet or second glass sheet, held in an aluminum frame with a junction box on the back. Thin-film panels replace the silicon wafers with thin layers such as cadmium telluride or CIGS on glass (DOE).

The panel is made by purifying silicon, growing it into crystals, slicing it into wafers, turning the wafers into cells, then laminating the cells into a framed module. Thin-film panels skip the wafer steps and deposit absorber layers directly on glass.

The crystalline silicon supply chain, in order:

1. Polysilicon: silicon derived from quartz is purified to a very high grade.
2. Ingots: for monocrystalline cells, a seed crystal is pulled slowly from molten silicon to grow one large single crystal, the Czochralski method developed by Polish scientist Jan Czochralski in 1918 (DOE timeline).
3. Wafers: the ingot is sliced with diamond wire into very thin wafers.
4. Cells: wafers are textured to trap light, doped to form the p-n junction, coated with an anti-reflective layer and printed with metal contacts.
5. Modules: cells are soldered into strings, sandwiched between encapsulant layers, a glass front and a backsheet or second glass sheet, then framed and fitted with a junction box.
6. Testing: each module is flashed under simulated sunlight to measure its rated power.

History of the photovoltaic cell

The photovoltaic cell went from a laboratory curiosity in 1839 to a 6%-efficient silicon device in 1954 and to lab records above 34% for tandem cells today. Each jump came from a new material or a better understanding of the p-n junction.

Edmond Becquerel first saw light raise the current in an electrolytic cell in 1839, and Adams and Day showed in 1876 that solid selenium could turn light into electricity (DOE solar timeline). Selenium cells stayed too weak for real power. The modern cell was born at Bell Labs, where Daryl Chapin, Calvin Fuller and Gerald Pearson built a diffused silicon p-n junction and published it in the Journal of Applied Physics (Chapin, Fuller & Pearson, 1954). Bell Labs announced it on April 25, 1954, at about 6% efficiency (APS News).

Progress was quick: Hoffman Electronics reached 14% in 1960, and Sharp produced practical silicon modules in 1963 (DOE). In 1961 William Shockley and Hans-Joachim Queisser published the detailed-balance limit that still frames single-junction research (Shockley & Queisser, 1961). Thin films followed: RCA’s David Carlson and Christopher Wronski made the first amorphous silicon cells in 1976, and a University of Delaware thin-film cell passed 10% in 1980 (DOE).

Since 1993, Martin Green and colleagues have published independently confirmed records in the “Solar cell efficiency tables” (Green & Emery, 1993), now beyond Version 67 (Green et al., 2026). The newest family, metal-halide perovskites, started with a 3.8% cell reported by Akihiro Kojima, Tsutomu Miyasaka and co-workers in 2009 (Kojima et al., 2009); stacked on silicon, perovskites now hold the 34.85% flat-plate tandem record (LONGi).

Year	Milestone	Source
1839	Becquerel observes the photovoltaic effect	DOE
1876	Adams and Day: selenium produces electricity in light	DOE
1918	Czochralski develops single-crystal growth, later used for silicon wafers	DOE
1954	Bell Labs silicon p-n junction cell, about 6%	J. Appl. Phys.
1960	Hoffman Electronics reaches 14%	DOE
1961	Shockley-Queisser efficiency limit published	J. Appl. Phys.
1976	First amorphous silicon cells (RCA)	DOE
1993	First “Solar cell efficiency tables”	Prog. Photovolt.
2009	First perovskite solar cell, 3.8%	JACS
2022	47.6% four-junction concentrator cell	Fraunhofer ISE
2025	34.85% perovskite-silicon tandem, certified by NREL	LONGi

Scientific references

• Chapin, D. M., Fuller, C. S. & Pearson, G. L. (1954). “A new silicon p-n junction photocell for converting solar radiation into electrical power.” Journal of Applied Physics, 25(5), 676–677. doi:10.1063/1.1721711
• Shockley, W. & Queisser, H. J. (1961). “Detailed balance limit of efficiency of p-n junction solar cells.” Journal of Applied Physics, 32(3), 510–519. doi:10.1063/1.1736034
• Green, M. A. & Emery, K. (1993). “Solar cell efficiency tables.” Progress in Photovoltaics: Research and Applications, 1(1), 25–29. doi:10.1002/pip.4670010104
• Green, M. A., Dunlop, E. D., Yoshita, M., et al. (2026). “Solar cell efficiency tables (Version 67).” Progress in Photovoltaics: Research and Applications, 34(4), 482–496. doi:10.1002/pip.70068
• Kojima, A., Teshima, K., Shirai, Y. & Miyasaka, T. (2009). “Organometal halide perovskites as visible-light sensitizers for photovoltaic cells.” Journal of the American Chemical Society, 131(17), 6050–6051. doi:10.1021/ja809598r

Bottom line

Photovoltaic cells turn sunlight into electricity through the photovoltaic effect: photons free electrons in silicon, and the p-n junction’s electric field drives them into a circuit as DC power. Monocrystalline silicon, increasingly TOPCon, heterojunction and back-contact designs, dominates the market, while perovskite-silicon tandems have pushed lab records to 34.85%. A full system adds an inverter, racking, wiring and often a battery. To see how many panels your home needs, try the solar panel calculator.