Re: Solar Cell Efficiency

From: Mike Yarwood (mpyarwood_at_btopenworld.com)
Date: 03/27/05 

Date: Sun, 27 Mar 2005 13:52:30 +0000 (UTC)

"Bill Kaszeta / Photovoltaic Resources" <bill@pvri_remove_.biz> wrote in
message news:4240dbfe.12998157@news.west.earthlink.net...
> On 22 Mar 2005 10:00:46 -0800, the1stlight@hotmail.com wrote:
>
>>Before I get started, I'd just like everyone to know that I am not a
>>scientist or professor or whatnot. I am a 17-year old high school
>>student with an interest in physics and engineering, so if i say
>>something that doesn't make scientific sense, then don't attack me for
>>it. The reason that I ask is because i don't know to begin with.
>>
>>Is there any real feisible way to increase the efficiency of a solar
>>panel? Because of the nature of solar energy, with the photons adding
>>energy to the electrons of a photoconductor to knock them out, isn't
>>the probability of a collison from a photon to an electron extremely
>>low? Is there any way to possibly contain the electrons within a region
>>that we can blast with light? Someone get back to me on this.
>>
> Efforts to increase solar cell efficiency include:
>
> 1. Multi-junction cells. The energy carried by a photon varies with
> wavelength and any energy above the bandgap of a junction
> is essentially lost as heat resulting in lower efficiency. Multi-
> junction solar cells are designed such at higher energy photons
> are absorbed in the first junction that has a higher bandgap while
> lower energy photons pass through to a lower bandgap junction.
> Problem is that the current through these now series connected
> layers is limited by the layer with the lowest current generation.
> The proportion of photon energies varies with time of day and
> season, making for complications.
>
> 2. Defects within solar cells (crystal dislocations, etc.) absorb
> electrons. High purity is better, but cost more.
>
> 3. There are tradeoffs between the doping of the semiconductor
> and the conductivity.
>
> 4. Then there is the problem of the front contact that has to allow
> light into the solar cell while making a low resistance connection.
> The lower percentage of grid covering (more light), the higher
> the losses due to series resistance.
>
> There are both efficiency and cost tradeoffs. A simple one is
> gold vs copper for grids. Concentrating the sunlight increases
> the output per solar cell but adds the need for the lenes, etc.
> and to aim the lens at the sun.
>
> Hope this helps.
> Bill Kaszeta
> Photovoltaic Resources Int'l
> Tempe Arizona USA
> bill@pvri-removethis.biz
Hi people!
Is there a nice range of differently tuned solar cells then so you might use
a reflector to feed a light pipe then split the output through prisms or
diffraction grating so each operated in its most efficient band?
Best of Luck - Mike

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