Absorption: intake of light by a material: the darker the material, the more light it absorbs

Acceptor: material which accepts electrons

Atomic shell: negatively charged electrons, which – figuratively speaking – orbit the nucleus (see below)

Atomic nucleus: motionless, positively charged centre of the atom

Defect electron: see hole

Donor: material which donates electrons

Doping: systematic addition of impurities into a high-purity material in order to manipulate the material properties such as electrical conductivity

Efficiency: ratio of energy used to energy spent: in lamps ratio of light produced to electrical power consumption, in solar cells ratio of electrical power produced to absorbed radiation power

Electron: negative charge carrier

Electron-hole pair: see exciton

Energy gap: energy range which is inaccessible to electrons

Exciton: excited state of a molecule in which an electron is lifted from the HOMO to the LUMO; equivalent to an excess electron and a missing electron (hole, defect electron) in the same molecule

Semiconductor: a material which, in its high-purity form, is electrically insulating, but can be made conductive through addition of impurities or elevated temperatures

HOMO: short for ‘highest occupied molecular orbital’

Kilowatt, kW: 1000 watts, see watt

Kilowatt-hour, kWh: 1000 watt-hours, see watt-hour

kW: see kilowatt

kWh: see kilowatt-hour

LED: short for ‘light emitting diode’

Hole (or defect electron): a missing electron, which, due to the positive charge of the nucleus, leads to the atom / molecule having an overall positive charge

LUMO: short for ‘lowest unoccupied molecular orbital’

Molecule: several atoms can link together to form a molecule which then has entirely new properties

OLED: organic LED, see also LED

Orbital: orbit of a negatively charged electron around the positively charged nucleus

Organic: chemical definition: material based on carbon (more exactly: hydrocarbon)

Proton: positively charged particle in nucleus

Photovoltaic: electrical power generation by light

Solar electricity: electricity produced by sunlight, either photovoltaic or solarthermal

Solar heat: heat production by sunlight, either for direct use of the heat or for power generation in a conventional steam power plant

Voltage: difference in electrical potential between a negatively charged area with excess electrons and a positively charged area with electron depletion or excess holes

Current: moving charge carriers (electrons and/or holes)

Sublimation: direct phase change from solid to gaseous phase, see also footnote in the text

Melting: phase transition from solid to liquid; evaporation: phase transition from liquid to gas

Substrate: carrier material, e.g. glass, plastic foil or metal foil

Watt: unit of electrical power, a bright light bulb uses up to 100 Watt when switched on

Watt-hour: unit of electrical energy/work, corresponds to the electrical power of one watt being produced over the course of one hour

2012 by OES, Johannes Widmer