Broad VF range of LED... 5-9V?
You shouldn't drive an LED with a voltage source.

You need to use a current source at up to 150mA

A resistor from a voltage significantly higher than the LED voltage is usually acceptable for low power applications although the current won't be as well defined as a proper current source.

The data sheet is telling you that when you drive the LED at the specified current (150mA in this case) the voltage across the LED could be anywhere between 5V and 9V.

If you use a voltage source such as 9V there could be enough variation between devices such that one operates correctly whole another has much higher current that exceeds the safe limit for the device thus destroying it.

Similarly, if you used 5V some LEDs would give out the specified amount of light but another might not give very much at all. The behaviour will also change over temperature or as the LED warms up during operation.