An innovative electrode tool now allows precise measurement of energy levels in OLED semiconductors, for improved efficiency and longevity in organic electronics.
A new study done by researchers of Institute of Computational Physics, Zurich University of Applied Sciences, Switzerland presents a cutting-edge integrated reference-counter electrode (IRCE) that refines the electrochemical characterisation of frontier energy levels in small-molecule thin-film semiconductors, a vital component of organic light-emitting diodes (OLEDs). Developed by researchers aiming to address the complexities of accurate measurement, the IRCE leverages a gel polymer electrolyte embedded with a silver quasi-reference electrode, streamlining analysis and potentially offering valuable insights for OLEDs and similar organic electronic applications.
OLED technology demands precise determination of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels for effective device modeling and performance optimisation. The study calibrated the IRCE using ferrocene, an internal standard, to establish an absolute energy reference. Comparative stability tests confirmed the IRCE’s reliability, aligning it closely with the traditional Ag/AgNO3 reference electrode while presenting a more streamlined and flexible approach for electrochemical measurements.
The IRCE assembly was rigorously tested using cyclic voltammetry on several OLED semiconductor materials, including NPB, TCTA, PO-T2T, and an NPB:PO-T2T exciplex. The materials exhibited distinct responses, underscoring the IRCE’s sensitivity to various molecular interactions. NPB, a widely-used OLED material, showed consistent and stable HOMO level readings that aligned well with those derived from traditional techniques, like UV photoemission spectroscopy. This alignment demonstrates the IRCE’s capacity to reliably replicate complex, high-accuracy measurements.
For materials like TCTA, the IRCE revealed signs of electropolymerisation, indicating a potential avenue for in-situ monitoring of chemical changes. Such insights are significant for researchers working on organic semiconductors, as the IRCE provides a practical approach for observing interactions directly within the thin-film context. Additionally, the HOMO level of the NPB:PO-T2T exciplex displayed minor shifts, highlighting molecular interactions within the exciplex structure—findings that could inform OLED efficiency improvements.
The IRCE’s versatility makes it particularly suitable for researchers and engineers developing organic semiconductors for OLEDs, organic solar cells, and other electronic devices. The device offers a practical method for determining HOMO and LUMO levels directly within thin films, enhancing research efficiency and precision. With applications extending across organic electronics, this study positions the IRCE as a valuable asset for advancing both the research and practical implementation of OLED technology.
