My screen is black after water drop - iPhone 4

Hi,

My Iphone 4, which i got as a replacement from Apple service center, i was using it for an year without any problem. One fine day i just cracked the front screen by dropping it down, but it was still working fine, I was just planning to replace the front screen. Unfortunatly before doing so my iphone 4 had a water drop, before i could switch it off ASAP, the screen blinked twice or thrice and the display gone. I could not able to switch it off, i put it in rice bag. After some 48 HRS,when i switch on the phone, there was literally no display on it, but holding the home button activates the voice control. Thus the verdict is the phone is working, but i could not able to see anything on the screen, i was following the 10-15 secs of Home+Power button method but of no use, except i could able to see the apple logo, but it is very very dim. Please help, what could be the problem? Battery or Display ? any way i have to change the display as the front screen is damaged already.