It's been coined "hygroelectricity", which means "humidity electricity", and scientists are already in the early stages of developing devices to harness it. What is "it" exactly? "It" is electrically charged water droplets hanging in the atmosphere.
Photovoltaic cells printed on sheets aren't news, nor are LEDs and ultrathin lithium batteries. What's news is a combination of the three which can help give light to 1.5 billion people who live in impoverished areas without access to electricity.