Short-circuit current

The short-circuit current (Isc) is a crucial parameter in photovoltaics that indicates the maximum current flow of a solar module or a solar cell under standard test conditions (STC). It occurs when the two electrical terminals of the module are directly connected, resulting in a resistance close to zero ohms.

How is the short-circuit current generated?

When sunlight hits a solar cell, electrons are excited and flow through the material. Under short-circuit conditions, these electrons are provided with a direct path without having to build up a voltage. As a result, a maximum current flows, which is referred to as the short-circuit current.

Why is the short-circuit current important?

  • Power determination: The short-circuit current is one of the parameters needed to determine the maximum power of a solar module. Together with the open-circuit voltage (Uoc) and the maximum power point (MPP), it forms the power curve of the module.
  • Module characterization: The short-circuit current is an important parameter for characterizing solar modules. It provides insights into the efficiency of charge carrier separation and transport within the module.
  • Safety aspect: A short circuit in a photovoltaic system can cause damage if not limited by appropriate protective measures. The short-circuit current is therefore an important factor for sizing fuses and other protective components.

Factors influencing the short-circuit current:

  • Solar irradiance: The intensity of solar irradiance directly affects the short-circuit current. The more intense the irradiance, the higher the short-circuit current tends to be.
  • Temperature: The temperature of the solar cell also affects the short-circuit current. As temperature increases, the short-circuit current slightly rises.
  • Cell material: The type of cell material used (e.g., monocrystalline, polycrystalline, thin-film) influences the magnitude of the short-circuit current.
  • Module size: The size of the solar module is proportional to the short-circuit current.

Measurement of the short-circuit current:

The short-circuit current is measured under controlled conditions in a solar simulator. The solar module is exposed to a defined light intensity and spectrum. The short-circuit current is then determined using a suitable measuring device, such as an ammeter.

Relevant keywords: solar module, solar cell, standard test conditions (STC), open-circuit voltage (Uoc), solar irradiance