5 Optoelectronic Devices and Sensors
5.5 Solar cells

A solar cell is a PV (photovoltaic) device that converts into electrical energy the incident radiation.

Semiconductor based solar cells can be single p-n junctions, heterojunctions or multi-junctions.

Main semiconductors used in solar cell fabrication are Si and GaAs.

The solar cell efficiency is given as the relationship between the maximum electrical power respects to the total incident power of light.

(017)

Where Vm and Im are the coordinates of the MPP (maximum power point) at the device output, G is the irradiance (W/m2) and A is the active area of the device.

Crystalline Si based solar cells have achieved efficiencies up to 25 % and multi-junction solar cells working under concentrated light present efficiencies up to 43.5 %.

The solar cell efficiency as well as main parameters of the device are given by manufacturers at STC (standard conditions of work): AM1.5 spectrum, G = 1000 W/m2 and T = 25 ºC.

Solar cells are connected in series to form strings in PV modules. A PV module consists in one or more strings parallel connected.