I'd like to be able to assume any monitor with IPS has led lighting, but I don't think tech specs list if its LED or fluorescent tube. fluorescent tubes cause uneven lighting and typically aren't as bright as LEDs, So I'd like to think all Dell IPS are LED, but I don't know for sure.
"A monitor can be an LCD monitor, and use either LED or fluorescent tubes for the backlighting of the monitor. Just because a monitor uses LEDs for the backlighting doesn't mean it's not an LCD monitor, though. It's still called an "LCD monitor" because it uses the same LCD panel that older, non-LED-backlit monitors use."