Researchers indicated that perovskite materials can provide a greener alternative for fabrication of field-effect transistors.
Perovskite has been a potential material for fabricating next-generation solar cells and LEDs. Over the past years, solution-processed metal-halide perovskites have been a major focus of research into low-cost, high-efficiency solar cells and LEDs. Because of their ability to process at low temperatures, it provides a greener alternative to conventional silicon.
Researchers from University of Bath suggest that perovskite materials can also be used for fabrication of transistors. Transistors are the building block of all electronic devices, and it is due to its capability of switching.
Transistors consist of three terminals: Gate, Source and Drain. Electrons flow between drain and source terminals , and the flow of current is regulated by the voltage applied at the gate terminal. However, the presence of ions interferes with the flow of electric current, rendering the transistor inoperable, and perovskite materials are rich in ions. When an electric field is applied, these ions rush and block the current between source and drain.
Researchers from the University of Bath and the Max Planck Institute for Polymer Research (MPIP) in Germany have found a solution to this problem.
“Until now, the presence of ions in perovskites has rendered the use of perovskites in transistors challenging. We saw this as a shame since perovskites are very promising semiconducting materials,” said lead researcher Professor Kamal Asadi from the Department of Physics at the University of Bath.
He added: “At room temperature, the perovskite’s ions are pretty mobile. People have resorted to reducing the temperature to get perovskite transistors to work because at low temperatures, ions are less mobile. But in real-life applications, that would mean that our perovskite-based gadgets would only operate reliably in the fridge or in Antarctica.”
“We looked at the problem from a different angle. We modified the construction of the transistors instead of modifying the material, resulting in a transistor with an extra, auxiliary gate. Ions are then pushed to the auxiliary gate and fixed in position. Then, when you apply a gate electric field, the electrons now see the gate field, react to it, and an electron flow between the source and the drain is established.”
The auxiliary gate was created by depositing a ferroelectric layer onto the transistor. The ferroelectric layer induces a large surface charge that attracts ions and holds them in position, thereby freeing up the gate for the flow of electrons.
“Pushing the ions away from the transport channel can only be achieved with auxiliary gate materials that can induce large surface charges, such as ferroelectrics or electrolytes,” explained the first author of the paper, Dr Beomjin Jeong, from the Max Planck Institute for Polymer Research. “We chose ferroelectric polymers because of their compatibility and ease of processing on top of the perovskite layer.”
The research has been published in the journal Advanced Materials.