An architecture in which n- and p-type materials alternate laterally in the active film of a device with a spatial period of about a carrier diffusion length would lead to efficient (opto)electronic devices for photovoltaic energy conversion and switching, among others. Such an architecture, although difficult to achieve with conventional silicon-based schemes, is within reach using semiconductor nanocrystals, whose intrinsic size can be varied on a nanometer scale. A photovoltaic device whose active film contains single semiconductor n-type nanocrystals embedded in a conjugated polymer p-type phase would be one realization of the channel architecture. An npn transistor, where a single, semiconductor nanocrystal serves as emitter and collector (n-type) separated by p-type material, could exhibit significantly higher switching speeds than is possible with conventional devices. The channel architecture is particularly useful for devices which rely on low-mobility materials.