Technological strides are not necessary. PV is at least 35 times more efficient than biomass in converting solar energy to electricity today.  Improvements are being made as the industry expands at a very rapid rate.  We were growing at a compounded rate of about 35% per year until 2004 when we hit a 65% growth rate which should be matched this year and for the next 5 years.

What we need is volume production - The industry has not and is not expecting "breakthroughs." The technology has been known for over twenty years.

That said, improvements do continue. Check out SunPower (www.sunpowercorp.com). They have the most efficient PV modules on the market and the aesthetics of their 200 watt module are unmatched by any competitor.  They could dominate the US market in the next 2-4 years.