Materials science - Invisible circuits

Imagine the applications that invisible electronic circuits, including active components such as diodes and transistors, might have. To make them, we need invisible conductors of two types _ some in which the charge carriers are electrons (n-type), and others in which they are holes (p-type). Invisible n-type conductors have been relatively easy to make, but only now is there an invisible thin-film p-type conductor with a conductivity approaching that needed for real applications.