What many engineers once saw as a flaw in organic electronics could actually make these devices more stable and reliable, according to new research from the University of Surrey and JOANNEUM RESEARCH MATERIALS.
The paper, which will be presented at the IEEE International Electron Devices Meeting (IEDM) 2025, describes how embracing small energy barriers at the metal/semiconductor interface of organic thin-film transistors (OTFTs) can help them perform more consistently and operate more reliably over time.
Organic thin-film transistors (OTFTs) are a key component of what are thought to be the next generation of flexible and wearable electronics. They are lightweight, low-cost and printable on large areas, but their long-term stability has been a persistent challenge.
Dr Radu Sporea, Associate Professor in Power Electronics and Semiconductor Devices at the University of Surrey's Advanced Technology Institute, project leader of the study, said:
"For years, engineers have tried to remove contact energy barriers, and with good reason: more often than not, they hold back performance. Our research turns that idea on its head. We found that small, well-controlled barriers actually make the transistor's operation far more stable."
Working with collaborators in Austria and industry partners at Silvaco Europe, the team fabricated flexible transistors using a silver contact material, common in printed electronics, and demonstrated improved current uniformity between devices. Even at very low operating voltages (≤ -4 V), the transistors maintained stable performance, making them ideal for low-power and wearable applications.
The key to understanding the improved stability in the devices was enabled by exploring the novel 'multimodal transistor' (MMT) design with two gate electrodes, allowing separate control of current injection and flow. This separation makes the MMT an ideal test structure for confirming the physics behind contact-controlled operation.
Using advanced computer simulations, the researchers confirmed that when the contact barrier is kept low but significant, the transistor operates in a contact-controlled mode, where current flow is primarily governed by the semiconductor/contact interface rather than the channel. This makes the devices more resistant to voltage shifts caused by trapped charges and other ageing effects that typically affect devices that rely on the channel for operation by eliminating energy barriers at the contacts.
Dr Eva Bestelink, Senior Research Fellow at the University of Surrey's Advanced Technology Institute and lead author of the study, said:
"Our study opens up exciting design possibilities. By working with the material's natural properties instead of against them, we can make flexible electronics more robust, sustainable and easier to produce."
In future, the use of MMTs and their robust operation could simplify the pixel circuits used in next-generation OLED or microLED displays, reducing manufacturing complexity and improving energy efficiency.
Access to the equipment and expertise at JOANNEUM RESEARCH MATERIALS was facilitated through the "EMERGE" Project of the European Union's Horizon 2020 research and innovation programme.
Dr Barbara Stadlober, Principal Investigator at JOANNEUM RESEARCH MATERIALS, said:
"Our technological processes for organic electronics have been perfected for many years, enabling precise control of material deposition and properties. We are very pleased with these scientifically valuable and industrially relevant results."
