Realizing efficient electroluminescence from silicon nanocrystals

Abstract

Colloidal semiconductor nanocrystals (NCs) have received considerable attention for optoelectronic applications due to their high photoluminescence efficiency and broad spectral tunability. The solution processibility of semiconductor NCs permits the integration into hybrid light-emitting devices that use organic semiconductors as charge transport layers. These devices offer the potential for low-cost manufacture through wet-coating processes in the future. While electroluminescence (EL) from group II-VI and III-V NCs has been well studied, emission from group IV NCs including silicon (Si) has not been characterized as extensively. This work focuses on solving the challenges to realizing efficient EL from hybrid nanocrystal-organic light-emitting devices (NC-OLEDs) containing organic semiconductors and SiNCs that are chemically passivated with ligands. Starting from the macroscopic point of view, this work first aims to understand the relationship between the surface morphology of SiNCs and device performance using a traditional hybrid nanocrystal-organic device design. The inherent bottlenecks of these conventional devices are discussed as they relate specifically to EL from SiNCs. Consequently, new device architecture is proposed, separately optimizing each functional layer within the hybrid device structure, concluding with the establishment of design rules for device engineering. Furthermore, efforts are made to address the significant open question of how surface passivation impacts device performance. Such discussion provides another consideration at NC surface during the hybrid-device design. Finally, an overview for the future research direction will be discussed.