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Realizing the potential of ZnO with alternative non-metallic co-dopants as electrode materials for small molecule optoelectronic devices

: Kim, Y.H.; Kim, J.S.; Kim, W.M.; Seong, T.-Y.; Lee, J.; Müller-Meskamp, L.; Leo, K.


Advanced Functional Materials 23 (2013), No.29, pp.3645-3652
ISSN: 1616-301X
ISSN: 1616-3028
Journal Article
Fraunhofer COMEDD; 2015 ()

High performance indium tin oxide (ITO)-free small molecule organic solar cells and organic light-emitting diodes (OLEDs) are demonstrated using optimized ZnO electrodes with alternative non-metallic co-dopants. The co-doping of hydrogen and fluorine reduces the metal content of ZnO thin films, resulting in a low absorption coefficient, a high transmittance, and a low refractive index as well as the high conductivity, which are needed for the application in organic solar cells and OLEDs. While the established metal-doped ZnO films have good electrical and optical properties, their application in organic devices is not as efficient as other alternative electrode approaches. The optimized ZnO electrodes presented here are employed in organic solar cells as well as OLEDs and allow not only the replacement of ITO, but also significantly improve the efficiency compared to lab-standard ITO. The enhanced performance is attributed to outstanding optical properties and spontaneo usly nanostructured surfaces of the ZnO films with non-metallic co-dopants and their straightforward integration with molecular doping technology, which avoids several common drawbacks of ZnO electrodes. The observations show that optimized ZnO films with non-metallic co-dopants are a promising and competitive electrode for low-cost and high performance organic solar cells and OLEDs. ZnO thin films are optimized by co-doping of non-metallic dopants for high optical and electrical performance. The ZnO-based organic photovoltaic (OPV) cells and organic light-emitting diodes (OLEDs) show highly improved efficiencies compared to indium tin oxide (ITO)-based devices. The optimized ZnO films are very promising electrodes for highly efficient and cost-effective OPV cells and OLEDs.