Re: I want to increase the efficency of my PELTIER junctions .

A Peltier element is a junction of two materials that generate or absorb heat
when a current flows, and can thus be used for cooling or heating.
The amount of heat generated or absorbed depends on (among a few other
things like temperature) the Peltier coefficient of the two materials and the
amount of charge going through.
Thus, if you switch the power off (as in chopping), you'll get less overall
heating or cooling. The only way to generate/absorb more heat with the same
current is to change the materials of the element or change other parameters
that affect the efficiency of the element (you can find the formula with all
parameters in a textbook).

This is as much as I can say without fully understanding your setup. Maybe
you can tell me exactly what you are trying to do, with what equipment, and
what the problem is.

Hope this helps.

Greetings from Singapore,
    Frank Berauer