Are OLETs Outshining OLEDs?

By Owais AliReviewed by Louis CastelAug 5 2025

OLETs are gaining attention as strong contenders to traditional OLED displays, offering improved efficiency, easier manufacturing, and more flexible integration options. Their voltage-driven operation and planar design support simpler device architectures and make them well-suited for use with flexible substrates, an advantage that could drive the development of next-generation, cost-effective, high-performance optoelectronic devices.

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What are OLETs?

Organic light-emitting transistors (OLETs) are multifunctional optoelectronic devices that combine light emission and electrical switching within a single organic semiconductor structure. Their planar field-effect architecture enables concurrent control of charge transport, current modulation, and photon generation. This integrated approach eliminates the need for separate switching and light-emitting components, leading to streamlined circuit designs and improved device compactness and efficiency.

OLETs are compatible with low-temperature fabrication methods, including solution-based and vacuum deposition techniques. These techniques enable large-area processing on various substrates, such as plastic films, glass, and metal foils. This manufacturing flexibility enables scalable production, making OLETs well-suited for use in flexible displays, optical interconnects, and advanced sensing technologies.¹

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Working Principle

OLETs operate on the principle of controlled recombination of charge carriers within an organic semiconductor channel. In an OLET, the active layer sits between the source and drain electrodes, while a gate electrode (separated by a dielectric layer) controls current flow by adjusting the charge carrier density via an applied voltage.  

When voltage is applied, electrons and holes are injected from opposite electrodes and guided within the channel by the gate field. As these carriers recombine, they form excitons that emit light via radiative decay. The gate voltage enables precise spatial and intensity control of the emission zone, allowing OLETs to function as both a switch and a light source.

OLETs operate in either unipolar or ambipolar mode. In unipolar operation, only one type of charge carrier (either electrons or holes) dominates, with recombination occurring near the injecting electrode of the minority carrier. Ambipolar OLETs support the accumulation of both carrier types, allowing the emission zone to be spatially tuned within the channel by adjusting the gate bias.²

OLETs vs OLEDs

OLETs offer a range of functional and structural advantages that address several limitations inherent to OLEDs.

Unlike OLEDs, which rely on current-driven operation, OLETs can be switched on and off by applying a voltage alone. This enables the use of lower-performance thin-film transistor (TFT) backplanes, significantly reducing the cost of driving circuits and enabling flexible and wearable display technologies. Additionally, integrating switching and light emission within a single OLET device simplifies the overall circuit architecture, thereby decreasing fabrication complexity and manufacturing costs.

OLETs exhibit improved device longevity due to more balanced charge carrier injection and operation under optimized electrical conditions. Their emission color can be precisely controlled through molecular and supramolecular engineering, enhancing their applicability in both display and sensing systems.

Trilayer OLET architectures have achieved external quantum efficiency (EQE) values of up to 5%, compared to 2.2% for OLEDs utilizing the same emissive and transport materials. These improvements are attributed to reduced electroluminescence loss mechanisms inherent to the OLET architecture.⁵

OLETs can be manufactured in a variety of geometries and on a wide range of substrates, using fewer material layers than OLEDs. The inclusion of a dielectric layer helps minimize sensitivity to defects like pinholes and electrical shorts. Additionally, OLETs offer higher brightness in both top- and bottom-emission setups.

As voltage-driven devices, OLETs exhibit lower power consumption and improved compatibility with commercial integrated circuits, enabling efficient integration into complex electronic architectures.^6,7

Impact on Devices and Consumer Benefits

OLETs offer considerable advantages for advanced optoelectronic devices, including the realization of transparent displays essential for applications in augmented reality, automotive systems, and biomedical devices.

They also exhibit superior control over emission patterns due to their planar device geometry, which enables directional light emission without the need for external optical elements. This feature is particularly advantageous for optical interconnects, on-chip communication systems, and lab-on-chip platforms, where precise spatial control of light is critical. Their compatibility with flexible substrates and low-temperature processing makes OLETs especially well-suited for the development of bendable and wearable optoelectronic systems.⁸

A notable advancement demonstrating OLET potential is the development of a plasmonic sensor system by European researchers in the EU-funded MOLOKO project. This system integrates an OLET, a nanostructured plasmonic grating (NPG), and an organic photodiode (OPD) within a single device. The innovative design enables highly miniaturized and cost-effective optical sensors without traditional optics, allowing unprecedented lateral proximity between light-emitting and detection modules, which enhances sensor performance. ⁸

This integration exemplifies the versatility and multifunctionality of OLET technology, underscoring its potential to revolutionize both display and sensing applications. As OLETs continue to advance, they are poised to enable a new generation of compact, efficient, and cost-effective optoelectronic devices.

This integration highlights the versatility and multifunctionality of OLET technology, reinforcing its potential to significantly impact both display and sensing applications. As the technology evolves, OLETs are expected to drive the development of a new generation of compact, efficient, and cost-effective optoelectronic devices.

References and Further Reading

1. Abbas, B., Sharma, K. (2022). Organic light emitting transistors: performance analysis and high performance device. Analog Integr Circ Sig Process 113, 383–391. https://doi.org/10.1007/s10470-022-02102-2
2. Makkonen, J. (2024). Organic light emitting transistors (OLETs). https://www.utupub.fi/bitstream/handle/10024/178990/Makkonen_Juho_opinn%C3%A4ytety%C3%B6.pdf?sequence=1
3. Ijeaku, A. M., Chidubem, M. H., Chukwunonyerem, E., & Obioma, N. (2015). Organic light emitting diode (OLED). Am. J. Eng. Res, 4(9), 153-159. https://www.academia.edu/16561031/ORGANIC_LIGHT_EMITTING_DIODE_OLED_
4. Hong, G., Gan, X., Leonhardt, C., Zhang, Z., Seibert, J., Busch, J. M., & Bräse, S. (2021). A Brief History of OLEDs—Emitter Development and Industry Milestones. Advanced Materials, 33(9), 2005630. https://doi.org/10.1002/adma.202005630
5. Muccini, M., & Stefano Toffanin. (2016). Organic Light‐Emitting Transistors. In Data Archiving and Networked Services (DANS). Royal Netherlands Academy of Arts and Sciences. https://doi.org/10.1002/9781119189978
6. Suppiah, S., Hambali, N. A. M. A., Wahid, M. H. A., Retnasamy, V., & Shahimin, M. M. (2018, February). Methodological comparison on OLED and OLET fabrication. In AIP Conference Proceedings (Vol. 1930, No. 1, p. 020055). AIP Publishing LLC. https://doi.org/10.1063/1.5022949
7. Soldano, C. (2020). Engineering Dielectric Materials for High-Performance Organic Light Emitting Transistors (OLETs). Materials, 14(13), 3756. https://doi.org/10.3390/ma14133756
8. Prosa, M., Benvenuti, E., Kallweit, D., Pellacani, P., Toerker, M., Bolognesi, M., Lopez-Sanchez, L., Ragona, V., Marabelli, F., & Toffanin, S. (2021). Organic Light-Emitting Transistors in a Smart-Integrated System for Plasmonic-Based Sensing. Advanced Functional Materials, 31(50), 2104927. https://doi.org/10.1002/adfm.202104927

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