Electroluminescence from hybrid ZnO/MgO core/shell nanowire/conducting polymer p-i-n devices

VEGA, NADIA; TIRADO, MONICA; COMEDI, DAVID

Paris

Simposio; 22th International Symposium on Metastable, Amorphous and Nanostructured Materials: ISMANAM 2015; 2015

INP Grenoble, FRANCE

Current efforts to obtain new optoelectronic materials with unique optical and electrical properties have led to intense research on the properties of hybrid nanostructured semiconductor materials. ZnO nanowires (NWs) are among the most promising nanostructures for the development of efficient optoelectronic devices, such as ultraviolet emitting LEDs, due to their large band gap and exciton binding energy. In addition, they have been shown to be suitable passive and active building blocks for transparent flexible electronics.In this work, we present a study of p-i-n heterojunctions made of n-type ZnO/MgO core/shell NWs and p-type conductive transparent polymers. Both materials are initially morphologically, electrically and optically characterized, by scanning electron microscopy, and by electrical conductance and photoluminescence measurements. The ZnO NWs were fabricated by a vapor transport method on n-type doped Si wafers and then coated by MgO for passivation of surface traps. Due to the particular growth mechanism in action, a ZnO NW layer is formed first on the Si substrate, from which the ZnO NWs grow nearly perpendicular to the substrate [1, 2]. Two different p-type conducting polymers were analyzed to be employed in this device: Pedot:Pss and Pedot:Tos. Then, hybrid p-n device structures with a novel architecture were constructed, where ZnO/MgO nanowires are embedded within Pedot conformal films, while the ZnO bottom layer conveniently avoids short circuiting between the Pedot and the conducting Si substrate. Both devices show good rectifying current-voltage characteristics. Furthermore, when a sufficiently high current under forward bias is injected, both devices exhibit electroluminescence in the UV. Finally, we present a model to interpret the results obtained. [1] N. C. Vega, R. Wallar, J. Caram, G. Grinblat, M. Tirado, R.R. LaPierre, D. Comedi. Nanotechnology 23, 275602 (2012)[2] G. Grinblat, L. J. Borrero-González, L. A. O. Nunes, M. Tirado, D. Comedi. Nanotechnology 25, 035705 (2014)