Synthesis of Nanoporous Thin Films without Substrate Oxidation – One Step Closer to Higher Efficiency Solar Cells

In conventional solar cells, one electron-hole pair is produced per solar photon absorbed. However, it has been shown that quantum dots are able to produce multiple electron-hole pairs per photon [Luque, 2007]. The difficulty with quantum dots is that they are not connected to anything. The focus here is to develop a method to make quantum wire arrays that can used to create multiple electron-hole pairs AND extract the current for next generation solar cells. The small uniform pore size (4 nm) [Urade 2007] and the facile transport through the pores [Wei 2007] of double-gyroid nanoporous thin films make them an ideal candidate to template quantum wires by electrodeposition. Synthesized by evaporation induced self-assembly of silica oligomers and a commercially available surfactant, the surfactant template of the nanostructured double gyroid film must first be removed before fabrication of the nanowire array can proceed. However, the surfactant template must be removed without oxidization of the substrate, and without degradation of the silica template to allow electrodeposition. Here, a procedure is reported to synthesis an organically modified silica source that is stable under liquid-phase surfactant extraction. These results bring us one step closer to higher efficiency solar cells.