ElectroHub
ComponentsActive / Semiconductor

Solar Cell / Photovoltaic

Optoelectronic

A large-area photodiode run in forward power-producing mode: light directly generates electricity. One silicon cell gives ~0.5–0.6 V regardless of size — area sets the current.

Schematic symbol

Photodiode

How solar cell / photovoltaic appears in a circuit diagram.

Types & variants

MonocrystallinePolycrystallineAmorphous/thin-film (works in low light)Epoxy-encapsulated hobby cellsFlexible cells

Key specs

Voc

V

Open-circuit voltage: ~0.6 V per silicon cell, cells stack in series.

Isc

A

Short-circuit current — proportional to area and light level.

Max power point

W

The knee (~80% of Voc) where the cell delivers most power.

Efficiency

%

Mono ~20%, poly ~17%, amorphous ~7% (but better indoors).

Laws that govern it

  • Shockley diode equation

    A solar cell is a large-area diode with an illumination current: its whole I–V curve is the diode equation shifted by the photocurrent.

  • Maximum power transfer theorem

    There is one point on that curve delivering the most watts — MPPT trackers exist purely to sit on it as light and temperature change.

  • Lambert's cosine lawE = (I / d²) × cos θ

    Output follows the cosine of the angle between the sun and the panel normal, which is why tilt and orientation matter as much as area.

Each law is stated in full — with its diagram, variables and worked meaning — on the electrical laws page.

Markings

Hobby cells print rated V/W at standard sun (1000 W/m²) — expect a fraction of that indoors.

Standard values

Hobby modules: 5 V/1 W, 6 V/2 W epoxy panels — sized so max-power voltage suits a charger IC.

How to choose

Count cells for the voltage you need under load (not Voc), then area for current. Amorphous for indoor/low light. Add a charger IC with MPPT for battery charging.

Pinout & package

Two terminals, + and −. Cells wire in series for voltage, parallel for current; shade on one series cell throttles the whole string.

Example circuits

  • Solar garden light (cell + Li-ion + charger + LED)
  • ESP32 weather station with solar top-up
  • Solar-powered calculator

Common failures

Cracked cells (output drops sharply), corroded tabbing wires, epoxy yellowing cutting output, and the ever-present 'partial shade' performance mystery.

How to test

In good light: Voc with a voltmeter (≈0.6 V × cell count), then Isc briefly in current mode. Both far below spec in real sun = damaged cell string.

Substitutes

Any panel of similar max-power voltage and equal-or-higher current; a USB power bank for prototyping while the solar side is debugged.

Where to buy

RobuAmazonAdafruitSparkFun