In the experiment, i cant use light to enhance the gas response, The light increased the current, but also decreased the response. according to many papers,the extra carriers should help to react with gas.
is there any part i didnt mention?
Most of the metal oxides used in gas sensors are wide bandgap materials so you need to use UV...... visible light will not lead to photoconductivity
Dear Pan,
There is something basic with the effect of light with suitable wavelength on the sensitivity S of the gas sensor. By definition the sensitivity of the gas sensor is the ratio of Rg the gas sensor resistance to an identical reference sensor R0.
So, S= Rg/Ro. R0 = L/sigma0 A, with L the length and A the area and sigma0 is the initial conductivity. Sigma= q u n, sigmao= qu n0
Then it results that the sensetivity S= n0/n,
Assume that n = n0-dn, where dn is the chang due to the gas adsorbed.
Finally we have S= n0/( n0-dn)= 1/ (1- dn/n0)
One would like make the ration dn/n0 as high as possible.
This accomplished by making n0 as small as possible such that dn can be an appreciable part of it by the adsorbed gas.
So, shining light will not help much but in contrary can make the sensor less sensitive.
Best wishes
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