Solution-grown nanowires make efficient lasers
A team at the University of Wisconsin-Madison in the US has reported an effective technique for growing ultra-small lasers from perovskites. The result, disclosed today in Nature Materials, is a shortcut to lasers that are extremely efficient and able to create many colours of light.
"While most researchers make these perovskite compounds into thin films for the fabrication of solar cells, we have developed an extremely simple method to grow them into elongated crystals that make extremely promising lasers," says Song Jin, a professor of chemistry at the University of Wisconsin-Madison. The rectangular crystals (known as nanowires) grown in Jin's lab are about 10 to 100 millionths of a meter long by about 400nm across.
The nanowires grow in about 20 hours once a glass plate coated with a solid reactant is submerged in a solution of the second reactant. "There's no heat, no vacuum, no special equipment needed," says Jin. "They grow in a beaker on the lab bench."
"The single-crystal perovskite nanowires grown from solutions at room temperature are high quality, almost free of defects, and they have the nice reflective parallel facets that a laser needs," Jin explains. "Most importantly, according to the conventional measures of lasing quality and efficiency, they are real standouts."
When tested in the lab of Jin's collaborator, Xiaoyang Zhu of Columbia University, the lasers were nearly 100 percent efficient i.e. every photon absorbed produced a photon of laser light. "The advantage of these nanowire lasers is the much higher efficiency, by at least one order of magnitude, over existing ones," says Zhu.
"These are simply the best nanowire lasers by all performance criteria," says Jin, "even when compared to materials grown in high temperature and high vacuum. Perovskites are intrinsically good materials for lasing, but when they are grown into high-quality crystals with the proper size and shape, they really shine."
The researchers say that simply tweaking the recipe for growing the nanowires could create a series of lasers that emit a specific wavelength of light in many areas of the visible spectrum.
Before these nanowire lasers can be used in practical applications, Jin says their chemical stability must be improved. Also important is finding a way to stimulate the laser with electricity rather than light, which was just demonstrated.
The collaborative research was funded by the US Department of Energy Basic Energy Sciences program.
