What Is Solar Cell?

What is a solar cell?

A solar cell is the elementary unit of every photovoltaic system. It is a thin slice of doped semiconductor material, almost always silicon in current commercial deployment, processed to create a p-n junction that drives electrons in one direction when light hits it. Each cell produces a small voltage (typically around 0.6 V at maximum power point for silicon) and a current proportional to the light hitting it. The total power of one cell is small, typically 6 to 13 W under Standard Test Conditions depending on cell size and technology.

Cells are wired in series inside a module to build up usable voltage. A typical residential module in 2026 contains 144 half-cut cells producing roughly 540 to 600 Wp at the module's nameplate. Modules in turn are wired in series into strings and parallel into arrays to build up the kWp of a full installation.

The cell is where solar physics happens. Everything else (module assembly, mounting, wiring, inverter, BOS) is engineering to extract the cell's electrical output reliably for 25-plus years. Innovation in solar over the last decade has been overwhelmingly at the cell level: PERC, TOPCon, HJT, and now perovskite and tandem cells represent successive improvements in how efficiently sunlight is converted.

Why solar cells matter

For solar EPCs, cell technology choice is the most consequential technical decision in module selection. Same wattage modules from different cell technologies behave very differently in Indian field conditions. A TOPCon cell with a lower temperature coefficient outperforms a PERC cell on hot summer afternoons. A bifacial cell picks up additional generation from albedo. These differences compound over 25 years.

For Indian manufacturers, cell capacity is the bottleneck that the PLI scheme is trying to address. India has had strong module assembly capacity for years, with imported cells often filling the supply gap. PLI-funded cell capacity expansion is changing that, with Adani Solar, Tata Power Solar, Waaree, Premier Energies, and others building integrated cell-to-module manufacturing.

For policy, cell origin is the key variable in DCR compliance. A module assembled in India from imported cells satisfies ALMM but not DCR. PM Surya Ghar requires DCR compliance, which means Indian-made cells. The cell is the upstream lever of India's solar manufacturing localisation.

For buyers, the cell technology in their modules determines long-term Performance Ratio. Two modules with identical nameplate Wp can deliver materially different lifetime kWh based on cell choice.

How a solar cell works

1. Silicon wafer. A polished silicon wafer (mono or poly) is the starting point.
2. Doping. One side is doped with boron (p-type), the other with phosphorus (n-type), creating the p-n junction.
3. Passivation. Surface layers (passivation films) reduce recombination losses where electrons would otherwise lose energy without producing current.
4. Anti-reflective coating. A thin coating reduces the fraction of incoming light that bounces off the cell.
5. Metallisation. Silver paste forms contact lines on the front (fingers and busbars) and the back. These collect the current.
6. Photon absorption. When light strikes the cell, photons with sufficient energy free electrons.
7. Charge separation. The p-n junction's electric field drives electrons to the n-type side and holes to the p-type side.
8. Current flow. Electrons flow through the external circuit (from cell to wire to load) and back to the p-type side. This flow is the DC current the system uses.

The same fundamental mechanism applies to all silicon cell technologies. The differences (PERC, TOPCon, HJT) lie in passivation strategies, contact materials, and cell-architecture variations that improve one or more of efficiency, temperature behaviour, or low-light response.

Real example: cell-to-module math for a typical Indian residential installation

Module specification. A 580 Wp residential module with 144 half-cut mono PERC cells.

Cell layout. 144 half-cut cells = 72 full-cell equivalents in series. Each half-cell produces about 4.03 W at maximum power point (580 ÷ 144). Maximum-power voltage per half-cell is about 0.62 V; current is about 6.5 A.

Module voltage. 144 half-cells × 0.62 V = roughly 89 V at maximum power point under STC. Open-circuit voltage runs higher, around 108 V.

Module current. Half-cut cells in two parallel strings of 72 each. Module maximum-power current is about 6.5 A.

String design. Twelve modules in series at the system level: 12 × 89 V = 1,068 V DC string voltage. That is too high for a residential inverter. Splitting into three strings of four modules each gives 356 V per string, which is well within typical residential inverter MPPT range.

The cell-level numbers cascade up to module specifications and string-design constraints. Field engineers do the math; buyers see the final installation.

Benefits of modern solar cells

• High efficiency. Modern mainstream Indian cells exceed 22 percent; premium TOPCon and HJT exceed 24 percent.
• Long lifetime. 25-plus years of operating output with minimal year-on-year degradation.
• Stable supply chain. Cell manufacturing is well-understood; capacity is expanding under PLI.
• Manufacturer accountability. Quality standards (IEC 61215, IS 14286) provide testing baselines.
• Multiple technology paths. PERC, TOPCon, HJT all serve different cost-performance points.
• Improving cost trajectory. Per-Wp prices have fallen significantly over the past decade.
• Indian manufacturing growth. DCR + PLI is building integrated Indian cell production.

Limitations of current solar cells

Efficiency ceiling. Silicon-only cells face theoretical efficiency limits (Shockley-Queisser limit around 33 percent for ideal single-junction silicon).

Temperature sensitivity. Silicon cells lose efficiency as temperature rises. Indian summer conditions stress this.

Degradation. Cells degrade slowly (0.5 to 0.8 percent per year); cumulative effect is roughly 20 percent loss over 25 years.

Shading sensitivity. A shaded cell drags down the rest of its string.

Manufacturing footprint. Cell production has its own environmental footprint, though far lower than thermal generation per lifetime kWh.

End-of-life recycling. Recycling infrastructure is still building out in India.

Solar cells in India

Aspect	Status
Dominant technology in 2026	Mono PERC, transitioning toward TOPCon
Typical cell size	182 mm and 210 mm half-cut
Mainstream efficiency	22 to 24 percent
Major Indian cell manufacturers	Adani Solar, Tata Power Solar, Waaree, Premier Energies, Reliance New Energy, Mundra Solar, others
DCR cell requirement	Indian-manufactured cells for subsidy-eligible projects
PLI for Solar PV	Demand-side incentive for Indian cell capacity expansion
Standard testing	IEC 61215, IS 14286 module-level qualification
Typical cell cost	30 to 40 percent of module cost

Quick facts

Term	Solar Cell (Photovoltaic Cell)
Function	Converts photons to electrical current via the photovoltaic effect
Material	Crystalline silicon (mono or poly) dominates commercial deployment
Typical size	182 mm or 210 mm wafer, half-cut variants common
Voltage per cell	Approximately 0.6 V at maximum power point
Power per full cell	6 to 13 W (technology-dependent)
Mainstream efficiency	22 to 24 percent
Premium efficiency	24 to 25 percent (TOPCon, HJT)
Lifetime	25-plus years operating output

Common mistakes about solar cells

1. Confusing cell and module. A cell is the smallest unit; a module is many cells wired together.
2. Buying on efficiency alone. Temperature coefficient, low-light response, and degradation matter as much for lifetime kWh.
3. Assuming all silicon cells perform the same. PERC, TOPCon, HJT differ in field behaviour.
4. Ignoring DCR cell-origin requirement. Indian-made cells are required for subsidy-eligible projects.
5. Comparing lab efficiency to commercial cells. Lab cells achieve 27 percent; commercial cells run 22 to 24 percent. The gap reflects manufacturing trade-offs.
6. Underestimating shading impact. Half-cut cells reduce but do not eliminate the shading penalty.
7. Forgetting that bifacial cells need light on both sides. Bifacial gain depends on installation and surface conditions.
8. Treating older poly cells as a current option. Mono PERC and TOPCon dominate. Poly is legacy.

Key takeaways

• A solar cell is the smallest unit that converts sunlight to electricity via the photovoltaic effect.
• Crystalline silicon dominates commercial deployment in 2026.
• Mainstream Indian cell efficiency runs 22 to 24 percent; premium TOPCon and HJT exceed 24 percent.
• Cells are wired in series to form modules; modules into strings; strings into systems.
• DCR requires Indian-made cells for subsidy-eligible projects.
• Cell technology choice drives long-term module performance and field kWh.
• Indian cell manufacturing is expanding under PLI for Solar PV.

Frequently Asked Questions

Sources

• IEC 61215. Crystalline silicon photovoltaic module qualification testing.
• IS 14286. Indian standard for terrestrial PV modules incorporating cell-level specifications.
• NREL Best Research-Cell Efficiency Chart. Reference efficiency benchmarks for cell technologies. nrel.gov
• Fraunhofer ISE. Photovoltaic research and cell technology reports.
• Indian Solar Manufacturers Association (ISMA). Indian cell manufacturing capacity reports.
• MNRE PLI Scheme for Solar PV Manufacturing. Operational guidelines and cell-capacity awards.
• Cell manufacturer technical datasheets. Specifications for current commercial cell technologies in India.