RESEARCH HIGHLIGHT - ‘Beautiful energy sandwich’ could power next-generation solar and lighting

Researchers have achieved a new level of control over the atomic structure of a family of materials known as halide perovskites, creating a finely tuned ‘energy sandwich’ that could transform how solar cells, LEDs and lasers are made.

Due to their remarkable 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 solar cells, LEDs and quantum technologies.

However, their instability and durability have, so far, largely limited perovskite devices to the laboratory. In addition, scientists have struggled to precisely control the thickness of perovskite films, and control how different perovskite layers interact when stacked together – an important step in building functional, multi-layered structures. Now, a team of researchers led by the University of Cambridge has found a new way to grow ultra-thin layers of perovskite films so their atoms line up perfectly, which could enable more powerful, durable and efficient devices.

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. Their results, reported in the journal Science, could open the door to usable perovskite devices that can be produced at scale, using a process like that used to make commercial semiconductors.

“A lot of perovskite research uses solution processing, which is messy and hard to control.”
“By switching to vapour processing — the same method used for standard semiconductors — we can get that same degree of atomic control, but with materials that are much more forgiving,”Professor Sam Stranks,  research co-lead, Dept of Chemical Engineering and Biotechnology

The researchers used a combination of three-dimensional and two-dimensional perovskites to create and control their atomically-tuned stacks, a phenomenon known as epitaxial growth. This fine control let the team directly observe how the light given off by the material changes 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. “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,” Dr Yang Lu, co-first author, Dept of Chemical Engineering and Biotechnology and Cavendish Laboratory

The researchers also found they could engineer the junctions between the layers to control whether electrons and holes stayed together or apart — a key factor in how efficiently a material emits light.

“We’ve reached a level of tunability that wasn’t even on our radar when we started. We can now decide what kind of junction we want — one that holds charges together or one that pulls them apart — just by slightly changing the growth conditions,”Professor Sir Richard Friend,  research co-lead, Cavendish Laboratory

Publication: Yang Lu, Young-Kwang Jung et al. ‘Layer-by-layer epitaxial growth of perovskite heterostructures with tunable band offsets.’ Science (2025). DOI: 10.1126/science.adx5685

University of Cambridge article

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