New solar cell solves durability problem

Northwestern University researchers developed a new solar cell that, they say, is cheap to produce, efficient and environmentally friendly.

It’s based on the Grätzel cell, which uses a molecular dye to absorb sunlight and convert it to electricity, and fixes its one big disadvantage: its tendency to leak. The dye-sensitized cell’s electrolyte is made of an organic liquid, which can leak and corrode the solar cell itself.

Grätzel cells typically last just 18 months, making them commercially unviable.

The Northwestern solution to this problem is a new material for the electrolyte that actually starts as a liquid but ends up a solid mass, making the cell inherently stable. A thin-film compound made up of cesium, tin and iodine, called CsSnI3, replaces the entire liquid electrolyte.

“This is the first demonstration of an all solid-state dye-sensitized solar cell system that promises to exceed the performance of the Grätzel cell,” says nanotechnology expert Robert Chang. “Our work opens up the possibility of these materials becoming state of the art with much higher efficiencies than we’ve seen so far.”

The Northwestern cell exhibits the highest conversion efficiency ever reported for a solid-state solar cell equipped with a dye sensitizer – approximately 10.2 percent.

“Our inexpensive solar cell uses nanotechnology to the hilt. We have millions and millions of nanoparticles, which gives us a huge effective surface area, and we coat all the particles with light-absorbing dye,” says Chang.

“This is only the beginning. Our concept is applicable to many types of solar cells. There is a lot of room to grow.”

The lightweight, thin-film structures are compatible with automated manufacturing, and the researchers now plan to build a large array.