Solar mobile charger

Hi,
i've worked recently on a project in uni. , using solar cells , and i found that it has a great potential especially where i live sun is abundant more than anything else

So i'm trying to use a solar cell its 6.5V , 170 mA at full sun light and drops to 140 mA in my Balcony but keeps a voltage of like 5Volts.

I'm trying to create a solar charger for my samsung star , but someone has any idea about how to simulate the usb the socket ?

also is this current enough for charging?

Thanks