The correct spelling of the term "dark current" is sometimes confusing to those who are unfamiliar with its pronunciation. The sound /k/ is represented by the letter "c" while the sound /ɑ/ is written using the letter "a". The final "t" denotes the syllabic ending, which is pronounced as a nasal sound. In phonetic transcription, the word "dark current" is written as /dɑrk ˈkɜrənt/. This refers to the small electrical currents that circulate in a device even in the absence of light.
Dark current refers to the flow of electrical current within a device or system in the absence of any external light stimulation. It is most commonly observed in electronic devices such as photodetectors, image sensors, and photovoltaic cells.
In photodetectors and image sensors, dark current is the unwanted electrical signal generated by thermal energy within the device's structure, leading to electron-hole pair generation and subsequent current flow. This occurs even without the presence of incident light. Dark current is primarily caused by the inherent random motion of electrons and thermal excitations within the material of the device. It is influenced by factors such as temperature and the composition of the materials used.
In photovoltaic cells, dark current is the reverse leakage current that flows when the cell is not exposed to light. It is due to a small fraction of electrons and holes recombining within the depletion region of the p-n junction. Dark current can reduce the overall efficiency of a photovoltaic system by increasing power losses and reducing the open-circuit voltage.
Minimizing dark current is crucial in many applications since it can lead to a higher noise floor, reduced sensitivity, and degraded image quality. Cooling the device, using specialized materials, and implementing appropriate biasing techniques are common methods employed to mitigate dark current effects.
The term "dark current" combines two words: "dark" and "current".
The word "dark" originated from the Old English word "deorc" which means "absence of light" or "without light". It has roots in the Proto-Germanic word "derkaz". Over time, the term "dark" has been widely used to describe something that is devoid of brightness or light.
The word "current" has its roots in Latin. It comes from the Latin word "currere" which means "to run" or "to flow". In the context of physics and electronics, "current" refers to the flow of electric charge through a conductor.
When these two words are combined, "dark current" refers to the flow of electric charge in the absence of light.