Organic Sandwiches Create Quantum Wells for Next Generation Electronics

November 18, 2019

Computational models created by Duke Engineers help researchers probe the properties of a new class of hybrid perovskite materials

Adapted from a press release from Purdue University

Neon green cubes on a black surface (left) and neon red cubs on a black surface (right)

Ultrathin hybrid perovskite quantum wells crystals exhibiting tunable optical properties. (Purdue University image/Letian Dou)

Materials scientists at Duke University have used their electronic structure based materials modeling software on a supercomputer to help demonstrate the advantages of incorporating uncooperative organic building blocks into a class of optoelectronic materials called hybrid perovskites.

The models showed that the new materials feature improved stability and safety while exhibiting a “quantum well” behavior that can improve the performance of optoelectronic devices such as solar cells, LEDs and optical computers, making the hybrid perovskites more attractive for use in a broad range of applications.

The results appeared online on November 11 in the journal Nature Chemistry.

Hybrid perovskites combine the best qualities of organic and inorganic materials to create new semiconductors suitable to broad applications due to their unique optical and electronic properties and low-cost manufacturing methods.

However, they also have some limiting characteristics. Their stability can be poor, causing them to perform well for a few hours or days, and then decay quickly. Furthermore, many recipes contain lead-based material, restricting their usability in wearable electronic devices.

Researchers around the world are constantly in search of new recipes for hybrid perovskites that can skirt around these limitations. In late 2018, Volker Blum, associate professor of mechanical engineering and materials science and of chemistry at Duke, and colleagues at Duke and at University of North Carolina-Chapel-Hill, demonstrated accurate electronic property predictions for a series of complex, layered hybrid perovskites using high-performance computing to help in this search.

Meanwhile, researchers at Purdue University led by Letian Dou, assistant professor of chemical engineering, developed a method for incorporating long, complex organic molecules into hybrid perovskites that previously would have been extremely difficult if not impossible to include. The method adds “side chains” to the organics to reduce the interaction between the organic molecules themselves, guiding how the organic molecules fit into the inorganic structure.

These complex organics possess semiconducting properties, allowing a thin layer sandwiched between inorganic layers to exhibit quantum well properties. These types of materials might be used to create compact, fast computer chips, highly efficient microscopic lasers and optoelectronic devices.

“These structures are very exciting,” said Dou of the new hybrid perovskites. “The sandwich structures are like those that are widely used today in many electronic and optoelectronic devices, but they are much easier to produce and more tolerant to defects.”

While the engineers at Purdue could engineer these new hybrid perovskites, they wanted to make sure they understood the electronic structure of the materials and that they would exhibit the desired quantum well behaviors. They turned to Blum and his supercomputer models to validate their expectations. And much to everyone’s delight, the models aligned well with the expectations and experimental results.

“These structures are conceptually similar to those for which we first demonstrated our approach in 2018, but realize the promise of extending it to a broader scope of organic molecules with desirable properties,” said Blum. “These are precisely the sorts of materials we were hoping our models would help advance.”

In further research, the Purdue team has already shown that these new hybrid perovskites can be made free of lead while exhibiting increased stability and performance in a field effect transistor (FET), an electronic device that uses an electric field to control the flow of current. FETs are used in integrated circuits in devices such as computers and wireless communications.

The potential uses for this type of material are broad because semiconductors are the foundation of essentially all electronic and optoelectronic devices like transistors, solar cells, LEDs, and photodetectors. The new organic-inorganic hybrid perovskite materials are cheaper and perform better than a traditional inorganic semiconductor. And the new materials design strategy could serve as a blueprint for many other functional hybrid materials.

“With our new technology, we can make the hybrid perovskite materials intrinsically more stable,” noted Yao Gao, a postdoctoral fellow in Dou’s research group. “By replacing the toxic lead, these new materials are better for the environment, and can also be safely used for bioelectronics sensors on the body.”

This research was supported by the U.S. Office of Naval Research, the National Science Foundation (jncluding the "HybriD3" project, NSF DMR-1729297, centered at Duke and focused on exploring new hybrid organic-inorganic semiconductors), the German Research Foundation and the Department of Energy Office of Science. An award of computer time was provided by the Department of Energy's Innovative and Novel Computational Impact on Theory and Experiment (INCITE) Program.

“Molecular Engineering of Organic-Inorganic Hybrid Perovskites Quantum Wells.” Yao Gao, Enzheng Shi, Shibin Deng, Stephen B. Shiring, Jordan M. Snaider, Chao Liang, Biao Yuan, Ruyi Song, Svenja M. Janke, Alexander Liebman-Peláez, Pilsun Yoo, Matthias Zeller, Bryan W. Boudouris, Peilin Liao, Chenhui Zhu, Volker Blum, Yi Yu, Brett M. Savoie, Libai Huang, Letian Dou. Nature Chemistry, 2019. DOI: 10.1038/s41557-019-0354-2