Cucumbers do need full sun to grow healthy and properly.
Even when cucumbers grow without full sun they sometimes grow just fine but when growing cucumbers the cucumbers will do much better when they are grown in full sun.
So it's best to plant the cucumbers in an area where the cucumbers can get the most sun.
Cucumbers do not do very well when they are in shade and don't have access to full sun.
When cucumbers do not get enough sunlight the cucumbers are more likely to have a poor fruit set and produce an overall lower yield.
So for best results you should plant the cucumbers where they'll get access to the most sun.