MIKROELEKTRONIKA 9.

Napelemek:1.Szerkezet és működés2.Alkalmazás3.Új megoldások

A nap minden masodpercben 6.1011 kg hidrogént alakít át héliummá, ami elég kb. 1010 évre. Az elektromágneses sugárzás tartománya 0,2-3 m.A Földre jutó energia kevesebb: veszteségek.

Ha a Nap 48* szögben áll, a beérkező energia 963W/m2. 1 km2 Szahara kap kb. 109 W !

Átalakítás:1.Direkt melegítés2.Biomassza, fotoszintézis3.Elektromosság

3.1. napelem (fotodióda)3.2. nanostruktúrák

Probléma: tárolás.

p-n átmenet mint napelem

ahol IL = Isc rövidre zárt áramkör árama ( a nemegyensúlyi elektronok árama), Is- a dióda telítési árama, RL -a terhelés, A - az átmenet felülete.

Ha I=0, nyitott áramkör, a feszültség:

Hatásfok: =

Teljesítmény:

Pmax ha dP/dV =0,

FF-fill factor:

Cells consisting of a single p–n junction that are made from bulk semiconductor have a maximum theoretical efficiency of 31% — and the best performing affordable commercial devices are about 18% efficient.

New DirectionsSurface structuring to reduce reflection loss: for example, construction of the cell surface in a pyramid structure, so that incoming light hits the surface several times.

New material: for example, gallium arsenide (GaAs), cadmium telluride (CdTe) or copper indium selenide (CuInSe²). Nanostructured, organic- biocomposites.Grätzel cells: Electrochemical liquid cells with titanium dioxide as electrolytes and dye to improve light absorption.

Si:(111) etching!

Amorf Si napelem: 5-6% Tandem napelem: 30%

The structure comprised a multiple-quantum-well (MQW) layer sandwiched between a p-type layer and an n-type layer. The MQW itself comprised 20 layers of gallium arsenide, each about 7.5 nm thick.

A solution of cadmium-selenium quantum dots, each just a few nanometres across, is deposited onto the structure. Inspired by photosynthesis:the photo-generated carriers within the quantum dots, which are confined within the etched channels, are close enough to the quantum wells that they can exchange energy via a dipole–dipole interaction. The patterned device was six times more efficient than the unpatterned one.