Photostrom

Photostrom, a term common in German-language literature, refers to the electric current produced in a device when it is illuminated with light. In English-language contexts the term photocurrent is used. It is a central observable in devices such as photovoltaic cells, photodiodes, and photoelectrochemical cells, indicating how efficiently absorbed light is converted into electrical energy or charge transport.

Mechanism: When photons with energy above the material’s bandgap are absorbed, electron-hole pairs are generated. In a semiconductor junction, an internal electric field or built-in potential separates the carriers and drives them toward contacts, resulting in a current in the external circuit. In dye- or organic-based devices, excitons must reach interfaces before dissociating to generate carriers. The magnitude and spectrum of the photostrom depend on light intensity, wavelength, device architecture, and material properties.

Measurement and performance: Photostrom is commonly reported as short-circuit current (Isc) under standard illumination, together with open-circuit voltage, fill factor, and overall power conversion efficiency in solar cells. Spectral responsivity, external quantum efficiency, and dark current are also used to characterize photostrom in detectors. Temperature, aging, and illumination conditions can affect the current through changes in recombination rates and contact resistance.

Applications and context: Photostrom is used to compare and optimize photoactive devices, to characterize light sensors, and to study fundamental processes in photoexcitation and charge transport. Understanding photostrom is essential for solar energy harvesting and for designing optoelectronic components with a desired spectral response. Related concepts include photocurrent, photoconductivity, and photoelectrochemical current generation.