By adjusting the levels of doping, doping material and the geometry (size, area) of a p-n junction diode, you can modify its electrical and optical behaviour.
It is a p-n junction diode with heavily doped p- and n-regions. It has a very narrow depletion layer (< 10 nm). It works on the principle of Zener breakdown mechanism.
Zener diode provides continuous current in reverse breakdown voltage region without being damaged. Its main use is in voltage stabilization or regulation.
It uses light (or photo) emitting semiconductor materials, with very thin p-region, whose thickness is determined by wavelength of radiation to be detected. It works on the principle of Photovoltaic effect.
Photo-diode converts an optical input into electrical current in reverse bias. It is used in receivers for remote controls in VCR & TV.
It is a p-n junction diode with materials having band energies corresponding to near infrared region or visible light region (GaAsP or InP). It works on the principle of Electroluminous. LED changes an electrical input to a light output in forward bias.
It is used in multimeters, digital watches, instrument displays, calculators, switch boards, burglar alarm and remote control devices.
It is a p-n junction diode in which either p or n region is made very thin to avoid significant absorption of light before reaching the junction. It works on the principle of Photovoltaic effect.
Solar cell is used for conversion of solar energy into electrical energy.