Subject: TiO2/ceramic solar devices

From: Dom <[email-masked]>
Date: Thu, 23 May 1996 22:37:18 -0400

All

Has anyone witnessed yellow TiO2?

I made some sol-gel TiO2 electrodes for a solar cell, and they turn yellow
over time under various conditions.  I attribute it to fluorecent emission
based on the spectral evidence.  It has an absorption max at 300nm, and a
weak emission peak at 700nm. 

My advisor is telling me that I have it all wrong despite the eveidence. 
He attributed it to band edge tailing due to surface states falling just
above the valence band. It does tail into the visible only slightly to
400nm, but exciting into this yeilds no detectable emission. Aside from
that if it were from just scatter like he was saying I would expect it to
be more green than canary yellow.

Has anyone else encountered this?  What did you make of it? 

Thanks,
Dom
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