D-pad down button on my ps3 controller not working any more

It has been 4 months since I gave my ps3 to a friend the controller was working good before i gave him now the d pad is not working but i found a temporary fix i had to charge the controller fully to make it work after I turn off the system I have to charge it again to make it work i was still happy then but now the button doesn't work any more any help? No water damage checked with my friend do I have to buy a new controller?