[Al Skierkiewicz]

Sorry,
I did miss that you were dealing with solar cells. As Dave and Dan have pointed out, these cells are a little different than batteries but not much. You can run in parallel without as much fuss as a regular battery. Unfortunately, the mismatch between 2 volts and 1.5 volts will still cause some losses and these losses could be catastrophic to the cells. Since you are dealing with currents in the 6 amp range, I think we can assume this is a fairly large array. I am also guessing that you are trying to get to a 12 amp supply for some design point. Have you considered a voltage multiplier running at a lower voltage? i.e. put all 7 cells in parallel for 42 amps and feed a 0.5 volt to 10 volt convertor. Even with the convertor losses, you still will be able to get a decent load current. However, adding an eighth cell would do the trick giving you 2 volts at 12 amps or 4 volts at 6 amps in series.
I would be remiss here if I didn't suggest you read some books on the care and feeding of solar cells. When you are dealing with currents this high, heat can be a serious issue and localized heat may cause cracking of the cell. When cracks occur, current production will drop. There is a really good Ham radio reference on solar cell use for powering remote transmitter sites. Let me ask around and see if I can turn up the title for you. It might also help if you let us in on some of your design criteria. What is the actual load?