Perovskite Materials: A Deep Dive into Their Vast Applications, From Electronics to Clean Energy

Scientists are taking a deeper dive into perovskite to better understand this material, which has vast applications covering electronics, energy storage, lasers, optoelectronics, glucose sensors, and more.

Scientists are taking a deeper dive into perovskite to better understand this material, which has vast applications covering electronics, energy storage, lasers, optoelectronics, glucose sensors, and more. But what is it exactly?

Perovskite is a natural mineral made of calcium, titanium, and oxygen with the crystal structure of CaTiO₃ or having the formula ABX3. It was first discovered in 1839 in Russia. A class of materials with the same crystal structure as the mineral perovskite are also known as perovskite materials.

The exceptional physical properties such as ferroelectric, dielectric, piezoelectric, and pyroelectric behavior and chemical properties, including catalytic activity and oxygen transport capability of perovskite, make them one of the most important structure classes in material science. This makes them a potential candidate for applications in fuel cells, memory devices, and photovoltaics.

They can also be used in solar cells to convert sunlight into electricity, as well as for the acquisition of clean energy and the degradation of organic pollutants.

Given all kinds of different industries, perovskite can potentially help advance, it makes sense that scientists are trying to understand it better.

Understanding Perovskite at Atomic Level for Better Control

Researchers from North Carolina State University, with support from the National Science Foundation, have discovered a way to create layered hybrid perovskites (LHPs) by studying them at the molecular level.

This breakthrough allows for unprecedented control over LHPs' light-emitting properties and can lead to significant advancements in laser and LED technologies. It also holds promise for engineering other materials for use in photovoltaic devices.

Layered hybrid perovskites (LHPs), according to the research, have emerged as promising semiconductors for next-generation energy and photonic applications. Here, controlling the distribution, size, and orientation of quantum wells (QWs) is extremely important.

LHPs are made up of very thin sheets of perovskite semiconductor material. These sheets are separated from each other by thin organic “spacer” layers.

Given that these thin films of multiple sheets of perovskite and “spacer” layers can efficiently convert electrical charge into light, LHPs have been of considerable interest to the research community for years. However, there is still limited understanding of how to engineer them to control their performance characteristics.

To understand them, we have to start with quantum wells, which are sheets of semiconductor material jammed between ‘spacer' layers.

They are the layers that form in LHPs. And a two-atom thick quantum well has higher energy than the one that is five atoms thick.

Because energy flows from high-energy structures to low-energy structures at the molecular level, we need to have three and four atoms-thick quantum wells between the two and five atoms-thick quantum wells, allowing the energy to flow efficiently.

“You basically want to have a gradual slope that the energy can cascade down.”

– Kenan Gundogdu, co-author of the paper and a professor of physics at NC State

However, people kept running into an anomaly when studying LHPs. The anomaly is the size distribution of quantum wells in an LHP sample observed through X-ray diffraction, which is different from what's detected using optical spectroscopy.

Aram Amassian, the paper's corresponding author and a professor of materials science and engineering at NC State University, illustrated how diffraction can indicate that quantum wells have a two-atom thickness and are part of a 3D bulk crystal. Meanwhile, spectroscopy can reveal that the quantum wells are two, three, and four atoms thick, in addition to the presence of the three-dimensional bulk phase.

So, the team went to look for answers: Why is there this disconnect between the two, and how can quantum wells' size and distribution in LHPs be controlled?

Through experiments, the team discovered nanoplatelets (NPLs) to be the key player. NPLs are individual sheets of perovskite material that form spontaneously on the surface of the solution the researchers used to create LHPs.

“We found that these nanoplatelets essentially serve as templates for layered materials that form under them,” said Amassian, noting that the atomic thickness of nanoplatelets dictates the thickness of LHP beneath it.

However, the nanoplatelets aren't stable, and their thickness keeps on growing, adding new layers of atoms over time.

“Eventually, the nanoplatelet grows so thick that it becomes a three-dimensional crystal.”

– Amassian

So, the anomaly was due to diffraction detecting the stacking of sheets but not nanoplatelets, while optical spectroscopy detects isolated sheets. He added:

“What's exciting is that we found we can essentially stop the growth of nanoplatelets in a controlled way, essentially tuning the size and distribution of quantum wells in LHP films.”

By doing so, researchers can attain superb energy cascades, which are essential for high reproducibility, low