(Northwestern University) The limitations of conventional and current solar cells include high production cost, low operating efficiency and durability, and many cells rely on toxic and scarce materials. Northwestern University researchers have developed a solar cell that, in principle, will minimize these limitations. In particular, the new solid-state solar cell is the first to solve the problem of the promising but leaky Grätzel cell. The device -- whose electrolyte starts as a liquid but ends up a solid mass -- is inherently stable.