This year’s winner of the Millennium Technology Prize, Michael Grätzel, director of the Laboratory of Photonics and Interfaces at Ecole Polytechnique Fédérale de Lausanne, has appeared often in Technology Review for his work developing dye-sensitized solar cells (also called Grätzel cells). The solar cells can be flexible, transparent, and tinted just about any color you’d like–features that make them attractive for consumer goods and windows. We wrote about the first product to use the devices last fall–a backpack with a solar panel attached to the back for charging portable electronics.

They’re not ready to replace crystalline silicon and cadmium-tellluride thin film solar panels, the kind sold today for rooftop and large-scale utility installations. Ultimately, when their cost is figured not by initial price, but rather the price divided by the total kilowatt hours produced during their warrantied life, they’re not yet cheap enough. But Grätzel and many other researchers are hard at work to make them more durable, cheaper to make, and more efficient.