I was watching one of my seniors soldering a few SMD LEDs on one of his power converters. He touched the iron on the anode of one of the LEDs and it glowed. I think it is because of thermal generation.
Later, I heard him talking about the LED not glowing if a current limiting resistor is present.
Am I correct in thinking that thermal generation of electrons might be the cause here? Also, I probably saw one of the LEDs glowing when the iron was touched on its cathode. Is this possible?