Space accumulation region

For a p-type semiconductor, (psc results from the excess negative charge associated with the ionized acceptors in the space charge region of the solid, and cpn is due to the accumulation of a positive ion layer ( 1 nm thick, from the solid surface) in the... 

Fig. 4.2 For an n-type bulk semiconductor in the presence of an electrolyte illustrated is (left) no space charge layer, (center) a space charge layer in a depletion region, (right) a space charge layer in an accumulation region.

Fig. 3.18 Types of space-charge region in an n-type semiconductor, dependent on the potential applied relative to the flat band potential, Un,. U represents potential (V) and Ec sur the electronic energy corresponding to Ec close to the surface, (a) c,sur = E no space-charge region (b) c,sur> E (U < U ) formation of an accumulation layer (c) c,sur formation of a depletion layer (d) c,sur efb (U U ) formation of an inversion layer.

To have passage of current it is necessary that EF is within the conduction or within the valence band in the space-charge region, i.e. accumulation layer in an n-type semiconductor (reduction) or hole accumulation layer in a p-type semiconductor (oxidation). 

Inside the silicon semiconductor, electrons diffuse from the n-type side (with a high electron concentration) in the direction of thep-type side. Holes diffuse from the p-side in the opposite direction. This results in a region where all charge carriers are depleted (space charge region). At thep-n junction both electrons and holes accumulate electrons on one side of the junction, and holes at the other side. Thus, a double layer of electric charges is formed, which leads to a potential difference of about 0.6-0.7 V. This is the solar cell s open-circuit voltage (OCV). When both sides of the... 

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