IV-VI nanocrystal-polymer solar cells

Processes are investigated for the fabrication of hybrid bilayer photovoltaic (PV) devices consisting of IV-VI nanocrystals (NCs) having near-infrared optical gaps and an organic conductive polymer. Our design utilizes PbS NCs spin-cast onto an indium tin oxide (ITO) coated glass slide, covered with a poly(3-hexylthiophene-2,5-diyl) (P3HT) layer. We demonstrate here that the removal of the surface ligand, by pre-rinsing the NCs and subsequent annealing, generates a smoother film with a greater degree of cross-linking between the NCs. Additionally, a post-production treatment enhances the interfacial layer and improves charge carrier separation and mobility, rendering better performing solar cells. Further, results using PbSe NCs indicate the method can be adapted to similar systems. The method proposed here was designed to optimize more independently the polymer and nanocrystal components of the device and, to an extent, the interface between them. (C) 2007 Elsevier B.V. All rights reserved.