At the Max Planck Institute for Polymer Research in Mainz, Tomasz Marszalek and his team have cracked a persistent problem in semiconductor engineering: getting perovskite crystals to arrange themselves in orderly layers. The breakthrough, published in the Journal of the American Chemical Society, centers on a deceptively simple idea—slowing down. By letting perovskite solutions dry gradually under solvent vapor instead of crystallizing rapidly, the researchers have created well-ordered two-dimensional structures suitable for high-performance transistors.
Perovskites are semiconductor materials with crystal structures that make them ideal for optoelectronic applications: solar cells, light-emitting diodes, and transistors. The catch is that their molecules need to arrange themselves in precise patterns, and conventional manufacturing moves too fast. The materials crystallize before they can self-assemble properly, much like trying to build a house when the foundation hardens before you've laid the bricks straight. This lack of control over crystallization has been one of the main barriers to broader perovskite use in electronics—devices that power everything from smartphones to washing machines.
Marszalek's innovation addresses this specifically for Dion-Jacobson perovskites, an especially challenging variant where organic and inorganic layers must form simultaneously in a more structurally demanding arrangement. Think of it as a burger where single layers of organic "cheese" must connect simultaneously to both the upper and lower "beef" layers of inorganic material, rather than building outward layer by layer. This creates a stronger final structure but demands exquisite control during assembly.
The team's method, solvent vapor-assisted drop-casting, slows crystallization dramatically, giving the building blocks time to arrange themselves into uniform, well-ordered structures. Working with collaborators from the Hong Kong Polytechnic University, the University of Toronto, and the Norwegian University of Science and Technology, the researchers systematically tested different organic molecules—called diammonium cations—that act as spacers and connectors between inorganic layers. These molecules varied in stiffness and symmetry, and the team used atomic force microscopy, X-ray diffraction, and electrical measurements to understand how each property influenced crystal structure and electrical conductivity.
The results were revealing. Particularly rigid and symmetrical molecules produced the greatest order in the two-dimensional Dion-Jacobson structures. That matters enormously for function: ordered structures allow electrical charge carriers to move through the material more efficiently, a decisive advantage for transistors that must switch and conduct current reliably billions of times per second.
The implications ripple outward. Perovskites are cheaper to produce than traditional semiconductors and their properties can be tailored precisely by adjusting their chemical composition. If transistors built from well-ordered perovskite layers can match or exceed the performance of conventional alternatives, the path to next-generation electronics becomes substantially clearer. The work lays a foundation for applications that have seemed promising in theory but elusive in practice.
What makes this advance particularly hopeful is its simplicity: controlling crystallization speed is far more elegant than fighting material chemistry. By working with perovskites rather than against their natural tendencies, Marszalek's team has shown how patience—and understanding—can unlock materials for technologies that shape modern life.