Rice University engineers have created microscopic seeds for growing remarkably uniform 2D perovskite crystals that are both stable and highly efficient at harvesting electricity from sunlight.
Halide perovskites are organic materials made from abundant, inexpensive ingredients, and Rice’s seeded growth method addresses both performance and production issues that have held back halide perovskite photovoltaic technology.
In a study published online in Advanced Materials, chemical engineers from Rice’s Brown School of Engineering describe how to make the seeds and use them to grow homogenous thin films, highly sought materials comprised of uniformly thick layers. In laboratory tests, photovoltaic devices made from the films proved both efficient and reliable, a previously problematic combination for devices made from either 3D or 2D perovskites.
“We’ve come up with a method where you can really tailor the properties of the macroscopic films by first tailoring what you put into solution,” said study co-author Aditya Mohite, an associate professor of chemical and biomolecular engineering and of materials science and nanoengineering at Rice. “You can arrive at something that is very homogeneous in its size and properties, and that leads to higher efficiency. We got almost state-of-the-art device efficiency for the 2D case of 17%, and that was without optimization. We think we can improve on that in several ways.”
Mohite said achieving homogenous films of 2D perovskites has been a huge challenge in the halide perovskite photovoltaic research community, which has grown tremendously over the past decade.
“Homogeneous films are expected to lead to optoelectronic devices with both high efficiency and technologically relevant stability,” he said.
Rice’s seed-grown, high-efficiency photovoltaic films proved quite stable, preserving more than 97% of their peak efficiency after 800 hours under illumination without any thermal management. In previous research, 3D halide perovskite photovoltaic devices have been highly efficient but prone to rapid degradation, and 2D devices have lacked efficiency but were highly stable.
The Rice study also details the seeded growth process—a method that is within the reach of many labs, said study co-author Amanda Marciel, a William Marsh Rice Trustee Chair and assistant professor of chemical and biomolecular engineering at Rice.
“I think people are going to pick up this paper and say, “Oh. I’m going to start doing this,'” Marciel said. “It’s a really nice processing paper that goes into depth in a way that hasn’t really been done before.”
The name perovskite refers both to a specific mineral discovered in Russia in 1839 and to any compound with the crystal structure of that mineral. For example, halide perovskites can be made by mixing lead, tin and other metals with bromide or iodide salts. Research interest in halide perovskites skyrocketed after their potential for high-efficiency photovoltaics was demonstrated in 2012.
Mohite, who joined Rice in 2018, has researched halide perovskite photovoltaics for more than five years, especially 2D perovskites—flat, almost atomically thin forms of the material that are more stable than their thicker cousins due to an inherent moisture resistance.
Mohite credited study co-lead author Siraj Sidhik, a Ph.D. student in his lab, with the idea of pursuing seeded growth.
“The idea that a memory or history—a genetic sort of seed—can dictate material properties is a powerful concept in materials science,” Mohite said. “A lot of templating works like this. If you want to grow a single crystal of diamond or silicon, for example, you need a seed of a single crystal that can serve as template.”
While seeded growth has often been demonstrated for inorganic crystals and other processes, Mohite said this is the first time it’s been shown in organic 2D perovskites.
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