As urgency to address climate change mounts, there’s ever greater interest in harnessing the unlimited potential of the sun to replace fossil fuels. This tantalizing prospect has inspired a raft of new scientific ventures, reports Stephen Forrest.

A theoretical field of silicon solar cells that is 120 miles on one side and 120 miles on the other, plunked down in a temperate zone, has the capacity to generate 20 terawatts of power. While such a solar array could more than address the needs of today’s global population, the scheme is impractical and the costs prohibitive. Silicon is expensive, says Forrest. “On the world market today, if you put a gallon of gas in your car, you’re paying 10 times less money than if the same energy were supplied through solar, due to the materials, production, packaging, installation and storage cost.”

So scientists are exploring how organic materials -- not living cells, but carbon-containing compounds -- might make solar power more economical. Organic photovoltaic cells, made of thin layers of fluorescing molecules, seem to hold out hope of an inexpensive alternative to silicon. But so far, these cells don’t offer the same kind of power efficiency as silicon-based technologies. Organic materials tend to break down over time, and present challenges in terms of reproducibility, scalability and reliability. While researchers are trying to manipulate these materials so they function better, an organic photovoltaic device to rival silicon remains out of reach.

But there’s much more optimism surrounding organically based lighting materials. Keep in mind that interior lighting consumes 20% of the power used in buildings, notes Forrest. Replacing incandescent bulbs would make a great difference in residential and commercial energy usage. Current compact fluorescents have long operational lifetimes, but may not be the most satisfying to the human eye. Make way for organic light emitting diodes (OLEDs), using molecules that when excited give off extremely bright light. Researchers have found combinations of chemicals that mix blues, greens and reds in pleasing ways, and these displays will soon emerge in next generation handheld gadgets and computer screens. Researchers are experimenting with white OLEDs, which appear to exceed the power efficiencies of incandescents, and at a low cost as well.