Stable electroluminescence from passivated nano-crystalline porous silicon using undecylenic acid

placing silicon-hydrogen bonds terminating the surface of nanocrystalline silicon with more stable silicon-PF carbon (Si-C) bonds. Hydrosilylation of the surface of partially and anodically oxidized porous silicon samples was thermally induced at about 90 degrees C using various different organic molecules. Devices whose surface have been modified with stable covalent bonds shows no degradation in the EL efficiency and EL output intensity under DC operation for several hours. The enhanced stability can be attributed to the high chemical resistance of Si-C bonds against cuffent-induced surface oxidation associated with the generation of nonradiative defects. Although devices treated with 1-decene exhibit reduced EL efficiency and brightness compared to untreatred devices, other molecules, such as ethyl-undecylenate and particularly undecylenic acid provide stable and more efficient visible electroluminescence at room temperature. Undecylenic acid provides EL brightness as high as that of an untreated device. (c) 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.