Highly efficient polaritonic light-emitting diodes with angle-independent narrowband emission

Authors acknowledge funding by the Volkswagen Foundation (no. 93404; M.C.G.), the Leverhulme Trust (RPG-2017-213; M.C.G), the European Research Council under the European Union Horizon 2020 Framework Programme (FP/2014-2020)/ERC grant agreement no. 640012 (ABLASE; M.C.G) and the Alexander von Humboldt Foundation (Humboldt Professorship; M.C.G.). A.M. acknowledges funding through an individual fellowship of the Deutsche Forschungsgemeinschaft (404587082; A.M.) and from the European Union’s Horizon 2020 research and innovation programme under Marie Skłodowska-Curie grant agreement no. 101023743 (PolDev; A.M.).Angle-independent narrowband emission is required for many optoelectronic devices, ranging from high-definition displays to sensors. However, emerging materials for electroluminescent devices, such as organics and perovskites, show spectrally broad emission due to intrinsic disorder. Coupling this emission to an optical resonance reduces the linewidth, but at the cost of inheriting the severe angular dispersion of the resonator. Strongly coupling a dispersionless exciton state to a narrowband optical microcavity could overcome this issue; however, electrically pumped emission from the resulting polaritons is typically hampered by poor efficiencies. Here we present a universal concept for polariton-based emission from organic light-emitting diodes by introducing an assistant strong coupling layer, thereby avoiding quenching-induced efficiency losses. We realize red- and green-emitting, narrowband (full-width at half-maximum of less than 20 nm) and spectrally tunable polaritonic organic light-emitting diodes with up to 10% external quantum efficiency and high luminance (>20,000 cd m−2 at 5 V). By optimizing cavity detuning and coupling strength, we achieve emission with ultralow dispersion (<10 nm spectral shift at 60° tilt). These results may have wide-reaching implications for on-demand polariton emission and demonstrate the practical relevance of strong light–matter coupling for next-generation optoelectronics, particularly display technology.Publisher PDFPeer reviewe

A substrateless, flexible, and water-resistant organic light-emitting diode

This research was financially supported from the Leverhulme Trust (RPG-2017-231), the EPSRC NSF-CBET lead agency agreement (EP/R010595/1, 1706207), the DARPA NESD programme (N66001-17-C-4012) and the RS Macdonald Charitable Trust. C.K. acknowledges support from the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2017R1A6A3A03012331). C.M. acknowledges funding from the European Commission through a Marie Skłodowska Curie individual fellowship (703387). A.M. acknowledges funding through an individual fellowship of the Deutsche Forschungsgemeinschaft (404587082). M.C.G. acknowledges funding from the Alexander von Humboldt Stiftung (Humboldt-Professorship).Despite widespread interest, ultrathin and highly flexible light-emitting devices that can be seamlessly integrated and used for flexible displays, wearables, and as bioimplants remain elusive. Organic light-emitting diodes (OLEDs) with µm-scale thickness and exceptional flexibility have been demonstrated but show insufficient stability in air and moist environments due to a lack of suitable encapsulation barriers. Here, we demonstrate an efficient and stable OLED with a total thickness of ≈ 12 µm that can be fully immersed in water or cell nutrient media for weeks without suffering substantial degradation. The active layers of the device are embedded between conformal barriers formed by alternating layers of parylene-C and metal oxides that are deposited through a low temperature chemical vapour process. These barriers also confer stability of the OLED to repeated bending and to extensive postprocessing, e.g. via reactive gas plasmas, organic solvents, and photolithography. This unprecedented robustness opens up a wide range of novel possibilities for ultrathin OLEDs.Publisher PDFPeer reviewe

A substrateless, flexible, and water-resistant organic light-emitting diode

Despite widespread interest, ultrathin and highly flexible light-emitting devices that can be seamlessly integrated and used for flexible displays, wearables, and as bioimplants remain elusive. Organic light-emitting diodes (OLEDs) with µm-scale thickness and exceptional flexibility have been demonstrated but show insufficient stability in air and moist environments due to a lack of suitable encapsulation barriers. Here, we demonstrate an efficient and stable OLED with a total thickness of ≈ 12 µm that can be fully immersed in water or cell nutrient media for weeks without suffering substantial degradation. The active layers of the device are embedded between conformal barriers formed by alternating layers of parylene-C and metal oxides that are deposited through a low temperature chemical vapour process. These barriers also confer stability of the OLED to repeated bending and to extensive postprocessing, e.g. via reactive gas plasmas, organic solvents, and photolithography. This unprecedented robustness opens up a wide range of novel possibilities for ultrathin OLEDs

Spectroscopic near-infrared photodetectors enabled by strong light-matter coupling in (6,5) single-walled carbon nanotubes

Strong light-matter coupling leads to the formation of mixed exciton-polariton states, allowing for a rigorous manipulation of the absorption and emission of excitonic materials. Here, we demonstrate the realization of this promising concept in organic photodetectors. By hybridizing the E11 exciton of semiconducting (6,5) single-walled carbon nanotubes (SWNTs) with near-infrared cavity photons, we create spectrally tunable polariton states within a photodiode. In turn, we are able to red-shift the detection peak which coincides with the lower polariton band. Our photodiodes comprise a metal cavity to mediate strong coupling between light and SWNTs and utilize P3HT and PC70BM as electron donor and acceptor, respectively. The diodes are formed either via mixing of SWNTs, P3HT and PC70BM to create a bulk heterojunction or by sequential processing of layers to form flat heterojunctions. The resulting near-infrared sensors show tunable, efficient exciton harvesting in an application-relevant wavelength range between 1000 nm and 1300 nm, with optical simulations showing a possible extension beyond 1500 nm

Spectroscopic near-infrared photodetectors enabled by strong light-matter coupling in (6,5) single-walled carbon nanotubes

Special Issue: Polariton Chemistry: Molecules in Cavities and Plasmonic Media. Funding: The authors gratefully acknowledge funding by the Volkswagen Foundation within project No. 93404. A.M. acknowledges further funding through an individual fellowship of the Deutsche Forschungsgemeinschaft (No. 404587082).Strong light-matter coupling leads to the formation of mixed exciton-polariton states, allowing for a rigorous manipulation of the absorption and emission of excitonic materials. Here, we demonstrate the realization of this promising concept in organic photodetectors. By hybridizing the E11 exciton of semiconducting (6,5) single-walled carbon nanotubes (SWNTs) with near-infrared cavity photons, we create spectrally tunable polariton states within a photodiode. In turn, we are able to red-shift the detection peak which coincides with the lower polariton band. Our photodiodes comprise a metal cavity to mediate strong coupling between light and SWNTs and utilize P3HT and PC70BM as electron donor and acceptor, respectively. The diodes are formed either via mixing of SWNTs, P3HT and PC70BM to create a bulk heterojunction or by sequential processing of layers to form flat heterojunctions. The resulting near-infrared sensors show tunable, efficient exciton harvesting in an application-relevant wavelength range between 1000 nm and 1300 nm, with optical simulations showing a possible extension beyond 1500 nm.Publisher PDFPeer reviewe

Influence of regioisomerism in bis(terpyridine) based exciplexes with delayed fluorescence

Exciplexes of individual electron donor and acceptor molecules are a promising approach to utilizing otherwise non-emissive triplet states in optoelectronic applications. In this work, we synthesize a series of bis(terpyridine) pyrimidine (BTP) isomers and employ them as electron acceptors in complexes with tris(4-carbazoyl-9-ylphenyl)amine (TCTA). We show that these TCTA : BTP complexes produce thermally activated delayed fluorescence (TADF) by exciplex emission, and we investigate the influence of the nitrogen position in the pyridine on the optical and electronic properties of the exciplex. The molecular arrangement of the complex is studied using scanning tunneling microscopy (STM) as well as classical force field and density functional theory (DFT) simulations. Finally, we fabricate organic light-emitting diodes (OLEDs) with maximum external quantum efficiencies ranging between 0.5% and 2% – depending on the BTP isomer

Weavable and Highly Efficient Organic Light-Emitting Fibers for Wearable Electronics: A Scalable, Low-Temperature Process

Fiber-based wearable displays, one of the most desirable requisites of electronic textiles (e-textiles), have emerged as a technology for their capability to revolutionize textile and fashion industries in collaboration with the state-of-the-art electronics. Nonetheless, challenges remain for the fibertronic approaches, because fiber-based light-emitting devices suffer from much lower performance than those fabricated on planar substrates. Here, we report weavable and highly efficient fiber-based organic light-emitting diodes (fiber OLEDs) based on a simple, cost-effective and low-temperature solution process. The values obtained for the fiber OLEDs, including efficiency and lifetime, are similar to that of conventional glass-based counterparts, which means that these state-of-the-art, highly efficient solution processed planar OLEDs can be applied to cylindrical shaped fibers without a reduction in performance. The fiber OLEDs withstand tensile strain up to 4.3% at a radius of 3.5 mm and are verified to be weavable into textiles and knitted clothes by hand-weaving demonstrations. Furthermore, to ensure the scalability of the proposed scheme fiber OLEDs with several diameters of 300, 220, 120, and 90 μm, thinner than a human hair, are demonstrated successfully. We believe that this approach, suitable for cost-effective reel-to-reel production, can realize low-cost commercially feasible fiber-based wearable displays in the future

Influence of regioisomerism in bis(terpyridine) based exciplexes with delayed fluorescence

A. L. S. acknowledges financial support through a Cusanuswerk scholarship. The authors acknowledge support by the state of Baden-Württemberg through bwHPC and the German Research Foundation (DFG) through grant no INST 40/575-1 FUGG (JUSTUS and JUSTUS 2 cluster). M. C. G. acknowledges support from the Leverhulme Trust (RPG-2016047) and the Alexander von Humboldt Stiftung through the Humboldt-Professorship. A. M. acknowledges support from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 101023743 (PolDev). C. B. acknowledges funding by the BMBF and the Ministry of Culture and Science of the German State of North Rhine-Westphalia (MKW) under the Excellence Strategy of the Federal Government and the Länder.Exciplexes of individual electron donor and acceptor molecules are a promising approach to utilizing otherwise non-emissive triplet states in optoelectronic applications. In this work, we synthesize a series of bis(terpyridine) pyrimidine (BTP) isomers and employ them as electron acceptors in complexes with tris(4-carbazoyl-9-ylphenyl)amine (TCTA). We show that these TCTA : BTP complexes produce thermally activated delayed fluorescence (TADF) by exciplex emission, and we investigate the influence of the nitrogen position in the pyridine on the optical and electronic properties of the exciplex. The molecular arrangement of the complex is studied using scanning tunneling microscopy (STM) as well as classical force field and density functional theory (DFT) simulations. Finally, we fabricate organic light-emitting diodes (OLEDs) with maximum external quantum efficiencies ranging between 0.5% and 2% – depending on the BTP isomer.PostprintPostprintPeer reviewe