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
Key specs
Voc
VOpen-circuit voltage: ~0.6 V per silicon cell, cells stack in series.
Isc
AShort-circuit current — proportional to area and light level.
Max power point
WThe knee (~80% of Voc) where the cell delivers most power.
Efficiency
%Mono ~20%, poly ~17%, amorphous ~7% (but better indoors).
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.