The controlled preparation and assembly of opto-electronic nanoscale materials is being tackled by top-down and bottom-up approaches. The latter draws inspiration from biology, where complex hierarchical systems are assembled from simpler building blocks. One of these, DNA, is proving especially useful: its size, stability, topology; the assorted chemical functional groups; plus its capacity for self-assembly provide a powerful nanoscale toolbox for materials preparation. Here we review recent research that shows the roles DNA can play in the preparation and organisation of semiconductor nanomaterials. Studies show that both hard inorganic and soft polymer materials can be directed to grow at nanoscale lengths using DNA and its constituents. In some cases the resulting materials have been used as components in simple electrical devices and the methodology has been extended to analytical tools. Intriguingly, these DNA–semiconductor hybrid materials have been found to self-assemble themselves, forming highly regular rope-like assemblies and conducting network structures.