The Peltier Effect is when the temperature of a P-N semiconductor interface increases or decreases in temperature due to the current flowing through the interface. The temperature change due to the Peltier Effect is dependant on which way the electrons are flowing. What I want to know is how the peltier effect can happen both ways. I've always been told that attaching a P type semiconductor to an N type creates a diode. Diodes only allow electrons to flow in 1 direction. Is the Peltier Effect a property of diodes, or are diodes something completely different?