From: John Woodgate
Subject: Re: Opposite of a photocell?
Date: Tue, 17 Dec 2002 07:53:48 +0000
Organization: JMWA Electronics Consultancy
Reply-To: John Woodgate
NNTP-Posting-Date: Tue, 17 Dec 2002 13:56:09 +0000 (UTC)
X-Newsreader: Turnpike (32) Version 4.01 <5Z8C9wtxbnpWyFnyfFzqmVF739>
I read in sci.electronics.design that J81 wrote (in
) about 'Opposite of a
photocell?', on Sun, 15 Dec 2002:
>I agree that you have found a solution for my application (thanks!),
>but I'm still curious about the existence of a device which has high
>resistance in light and low resistance in darkness.
It seems to me that such a device is thermodynamically improbable if
only one substance, such as silicon, is involved. You ask for the
addition of light energy to *reduce* electron mobility - reversibly.
I'm not saying it's impossible in more complex systems - photochromic
lenses show that reversible light-activated chemical reactions occur.
The dark compound has more internal energy, and is unstable in the
absence of light. Whether this type of chemical reaction can be arranged
to occur in, for example, an organic semiconductor material, in such a
way as to reduce electron mobility is an interesting question. Do you
have $1M to fund a research grant? (;-)
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
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