Date: Fri, 18 Oct 2002 08:28:43 -0400

Author: Sam Sampere

Subject: Re: Solar Cells and Cadmium Sulfide Cells


Yes and no. Don't worry about heating, because as the cell warms, the efficiency
improves. If you put red near the front surface, that layer will also absorb blue
light. You don't want to absorb blue light here. So put the blue absorber near
the front, it's transparent to red. The last layer absorbs the red. Whatever is
left after this first pass will have one more chance to be absorbed on the way
through again.

My cell is from Uni-Solar. Check them out at

They make some pretty cool products. I have an 11 W cell. Check out: to see the solar cell display. I
use quartz halogen work lamps. Nothing else puts out enough visible light to get
any appreciable power with the exception of the sun. And I tried them all!!!!!


Jerry DiMarco wrote:

> At 12:23 PM10/17/2002, you wrote:
> >...Companies use various other materials for earth based solar
> >applications. Mine is a triple junction thin film amorphous silicon solar
> >cell. Amorphous silicon is an excellent light absorber compared to
> >polycrystalline Si, so they can get by using thinner films. Triple
> >junction means that there are 3 active layers. One absorbs red, another
> >green, and the 3rd blue. Why not just build 'em so they absorb red? You
> >improve performance by absorbing the higher energy blue in a layer that
> >lets red pass. Then these 3 layers and all the individual cells are wired
> >together.
> >
> >The back side of this is a highly reflective surface which reflects unabsorbed
> >light through the layers again. This improves performance too.
> >
> >Ok, you are now the engineer, which active layer is closest to the sun, red,
> >green, blue? Why?
> >
> >Sam
> I guess there is a shortage of engineers on Tap-L. We'll have to do
> some recruiting. But it appears you alluded to the answer above. The
> information I have says shallow-diffused cells have a higher response to
> blue light than deep-diffused cells. It also says back surface reflector
> cells reflect the unused longer wavelengths which would otherwise overheat
> the cell and reduce performance. It sounds like the longer the wavelength
> - the deeper the penetration. So my guess is the blue sensitive layer is
> on top and the red is on the bottom.
> Now a question for you, where did you get your cells? Also meant to
> ask Dale, what are you using for a light source?
> Jerry
> <><><><><><><><><><><><><><><><><><><><><><><><><><><><><>
> Jerry DiMarco
> Manager of Lecture Demonstrations and Instructional Labs
> Montana State Univ., Physics Dept.
> Bozeman, MT
> Our Motto: "We don't use anything the way it was meant to be used."