From what I have heard, the efficiency of solar cells is at best about 40 percent or so. That is not good enough at current manufacturing costs to make it possible for the technology to compete with other forms of power that consumers can purchase. So, either the efficiency must increase or the cost to produce the cells must decrease. It
Professor W.S. Sampath from Colorado State University
a technique to create solar cells without the pricey silicon, therefore making the cells cheaper to make. However, it appears that the efficiency is not quite up to par yet with the current standards. In any case, the cost per watt of the power could potentially drop to the point that solar does become cost-effective for the average consumer to consider. That's good news, and maybe the efficiency could increase with more development, making this truly a win-win scenario.
[Source: Slashdot via