Perovskites have emerged as promising materials for light-emitting applications thanks to their photoelectric properties and have been touted as a cheap and flexible option for everything from solar cells to LEDs and fast X-ray detectors.
Now researchers have reported achieving a new level of control over the atomic structure of halide perovskites, which they described as creating a finely-tuned “energy sandwich”, something that could help with the development of more powerful, durable and efficient devices.
Because of their significant ability to absorb and emit light - and because they are cheaper and can be configured to convert more of the solar spectrum into energy than silicon - perovskites have long been touted as a potential replacement for silicon in some devices. But despite this promise, perovskite devices have largely been limited to the lab because of issues with stability and durability.
Controlling the thickness of perovskite films, and how different perovskite layers interact when stacked has also been a challenge.
Now, a team of researchers led by the University of Cambridge have reported that they have found a new way to grow ultra-thin layers of perovskite films so their atoms line up.
The researchers used a vapour-based technique to grow three-dimensional and two-dimensional perovskites one layer at a time, which enabled them to control the thicknesses of the films down to fractions of an atom.
They said their results could open the door to perovskite devices that can be produced at scale, using a process like that used to make commercial semiconductors.
Perovskites have so far proved difficult to control in layered devices, due in part to their chaotic atomic structure.
The researchers used a combination of three-dimensional and two-dimensional perovskites to create and control their atomically-tuned stacks. This let them observe how the light given off by the material changed depending on whether it’s a single layer, a double layer, or thicker.
“The hope was we could grow a perfect perovskite crystal where we change the chemical composition layer by layer, and that’s what we did,” said co-first author Dr Yang Lu from Cambridge’s Department of Chemical Engineering and Biotechnology and Cavendish Laboratory. “It’s like building a semiconductor from the ground up, one atomic layer after another, but with materials that are much easier and cheaper to process.”
The researchers also found they could engineer the junctions between the layers to control whether electrons and holes stayed together or apart. They could tune the energy difference between the layers by more than half an electron volt and in some cases, extend the lifetime of electrons and holes to over 10 microseconds. The research was published in the journal Science.
“Halide perovskites exhibit superior optoelectronic properties but lack precise thickness and band offset control in heterojunctions, which is critical for modular multilayer architectures such as multiple quantum wells. We demonstrate vapor-phase, layer-by-layer heteroepitaxial growth exemplified by CsPbBr3 deposition on single crystals of PEA2PbBr4 (PEA: 2-phenylethylammonium),” the paper said.
The team says this level of precision could pave the way for scalable, high-performance devices that use light in new ways, from lasers and detectors to next-generation quantum technologies.
More reading on perovskites
- Perovskite lighting [C&I premium content]
- Improved solar cells [C&I premium content]
- Enhancing perovskite solar cells
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