Hanbat National University researchers find way to improve OLED efficiency and lifespan

Organic light-emitting diodes (OLEDs) power many display screens, but their efficiency can be limited by energy lost inside the device. As organic layers are deposited, their molecules can align to create an internal electrical potential known as giant surface potential (GSP). When this potential draws excess positive charges, or holes, near the light-emitting layer, they can interfere with light-producing excitons. This process, called exciton–polaron quenching, reduces emitted light and can affect device performance. 

A research team was led by Professor Jae-Hyun Lee from the Department of Creative Convergence Engineering at Hanbat National University, Republic of Korea, along with Dr. Jong Soo Kim from the Samsung Advanced Institute of Technology. The researchers placed thin electron-blocking layers (EBLs) between the hole-transport and light-emitting layers to adjust the local electrical environment. They compared materials with negative GSP values of −1, −40 and −87 millivolts per nanometer, using electrical measurements, impedance spectroscopy, transient electroluminescence, and photoluminescence to examine charge movement and light loss. This paper was made available online on July 7, 2026, and was published in Volume 545 of the Chemical Engineering Journal on October 1, 2026. 

The measurements showed that negative GSP could counter the emitting layer’s positive potential and regulate unwanted hole injection. Impedance and transient electroluminescence data revealed that the stronger the negative GSP, the more holes were held at the interface with the emitting layer. The o-CBP layer, with a GSP of −40 millivolts per nanometer, provided the best balance in the tested devices. “The key is to control the interface potential between layers, rather than simply using a material with the strongest GSP,” said Prof. Lee. 

The strongest negative GSP was not the best option. PhCzCz-PhTPS, at −87 millivolts per nanometer, trapped holes strongly at the interface and also restricted charge injection too much. This reduced current and the likelihood of forming light-emitting excitons, lowering efficiency and shortening device lifetime. By contrast, the o-CBP device reached an LT95 lifetime of 35 hours, compared with about 29 hours for the reference, approximately 20% longer. LT95 measures the time for luminance to fall to 95% of its initial level under the study’s test conditions. “Our results show that an intermediate negative surface potential can reduce energy loss while preserving the charge flow needed for light emission,” said Prof. Lee. 

The findings suggest a design strategy for OLED technology: treat interfacial electrostatics as an adjustable property, not simply a consequence of the materials. Better control of charge accumulation could support energy-efficient displays and longer-lasting screens in smartphones, televisions, monitors and emerging foldable or wearable devices. However, these experiments tested OLEDs under laboratory conditions; they do not establish longer battery life, reduced burn-in, or improved image quality in commercial products. 

Overall, the study shows that negative GSP should be tuned to the surrounding layers, not maximized. This principle may also inform other organic electronics where interfacial charge accumulation contributes to energy loss. Further testing across device designs and operating conditions is needed to determine how broadly the approach can improve real-world display performance. 
 

Reference 
Title of original paper: Negative giant surface potential engineering for suppressing exciton–polaron quenching in organic light-emitting diodes  
Journal: Chemical Engineering Journal  
DOI: https://doi.org/10.1016/j.cej.2026.179183  

About the institute 
Hanbat National University, established in 1927, is a premier higher education institution located in Daejeon, Republic of Korea. Recognized as a glocal cooperative innovation university, it serves as an innovative platform bridging the region, industry, academia, and research sectors to create future value. Across its specialized campuses, including Yuseong Deokmyeong and Daedeok Industrial-Academic Convergence, the university offers practice-oriented education and cutting-edge research opportunities. Hanbat National University is fully dedicated to cultivating future-ready leaders and driving sustained regional innovation, ensuring the proud institution remains a hub of academic excellence and global competitiveness within the modern higher education ecosystem today.  
Website: https://www.hanbat.ac.kr/eng/ 

About the author 
Prof. Jae-Hyun Lee is a Professor in the Department of Creative Convergence Engineering at Hanbat National University, Republic of Korea. He earned his B.S. degree from Korea University in 2002 and a Ph.D. from Seoul National University in 2011. Following his doctoral studies, he conducted research as a post-doctoral fellow at the Institut für Angewandte Photophysik, Technische Universität Dresden, and has led the Organic Semiconductor Laboratory (OSEL) at Hanbat National University since 2012. His group studies how charges, excitons, and spins behave inside organic semiconductors used in displays and electronics, developing measurement methods that observe these processes directly. Current topics include interface polarization in OLEDs, exciton quenching by charges, spin-dependent light emission, the stability of charged molecules, electrical doping, and light extraction with nanostructured parylene films. An accomplished scholar, his extensive contributions to materials science include over 100 high-impact publications, over 2,500 citations and over 40 patents within the global scientific and academic fields.