clearing up on solar cells+black body radiation (1 Viewer)

[Steven12]

alrite this is my definition, if there is anything wrong with , please point out.


solar cells mainly of a n-type semicondutor layer, a depletion zone and a p-type semiconductor. when light(photons) reach n-type layer, it excites the electrons to conduction band, the metal grid surround the n-type collects the photoelectron and they flow into the external circuit to p-type, thus generating electricty.?

----------black body radiation and how planck explained it.

Black body is a theoretical concept that is able to absorb and emit radiation at maximum efficiency, a furnace with a cavity is an approximation. A heated black body contain a broad spectrum of wavelengths. classical scientifci theory predicts that as wavelength of radiation decreases, the energy density will approach inifinity, this violates conservation of energy.historically, this unrealistic prediction of energy density of short wavelengths EMR such as UV ray is termed UV castatrophe.

the predicted blackbody curve was proven wrong by experimental result, Planck found that he could only make sense of this experimental curve(bell-shaped curve with a peak) by proposing that energy of EMR is not distributed continously , but rather in packets of energy called quanta, he formulated his result to e=hf. ( i dont think i really need to explain the peak, its to do with electron unable to obtain large energy at high frequency i think) This effectively limited the energy output a an oscillatiing charge aand thus successfully explained the black body curve.

thats is a lota typing, feel free to correct me ....anything missin

 

[sub]

with the solar cell, dont u have to talk about the depletion zone and the electric field set up there?

 

[Steven12]

yea i suppose. a depletion zone to avoid further diffusion.

 

[helper]

Black Body is a more than you need as you only have to identify Planks hypothesis. Remember to draw a labelled diagram to explain the black bodyurve shape.

For the solar cells. The important bit to emphasis is the photoelectric part. The rest is normally not going to give you extra marks. So talk about quanta being totally absorbed. energy transferred to electron etc.

 

[Jase]

so.. light falls on boundary and electrons are excited from the semiconductor (ntype or ptype, i think in some cases, either can be used?) and into the other one to fill up holes. This set an intense electric field at the boundary and makes a current flow..?

 

[senso]

what about photocells?

 

[Xayma]

so.. light falls on boundary and electrons are excited from the semiconductor (ntype or ptype, i think in some cases, either can be used?) and into the other one to fill up holes. This set an intense electric field at the boundary and makes a current flow..?

Pretty much, the n-type on top, p-type on the bottom acts as a diode, which replaces the electrons knocked lose on the current.

It is easier for them to flow through the external circuit and travel that way then try and travel the opposite way through the diode region.

 

[Jase]

Ah okay, so when the n-type and p-type are joined, electrons from the n-type fill up the p-type, and then when the light hits the p-type, it knocks electrons out back into the holes of the n-type, so the current flows p to n like it should.

 

[Xayma]

No at the start all the electrons from the n-type jump to the p-type forming a localised +ve area on the n-type and a -ve region on the p-type. All electrons dont fill all holes so there are spare electrons and holes.

Then when light hits the n-type electrons are released, these flow through the circuit. With the hole moving towards the junction, these are filled by electrons at the junction.