Polycondensation enables designed synthesis of n-type organic/polymeric semiconductors .The frameworks reduce reorganization energy and induce interlayer electronic coupling .The frameworks achieve exceptional electron mobility. Electrons move in the framework in the lateral and vertical
directions. Exceptional electron conduction in two-dimensional covalent organic frameworks. Semiconductors are key elements in solar cells, light-emitting diodes, and thermoelectric generators where electron transport is the basic process, which governs their performance.
SUMMARY: Most organic/polymeric semiconductors are p-type semiconductors, whereas their n-type versions are limited in both availability and carrier mobility. How to develop high-rate n-type organic/polymeric semiconductors remains challenging. Here, we report an approach to high-rate n-type semiconductors via topology-directed polycondensation of conventional p-type knots with n-type isoindigo linkers to form non-conjugated tetragonal and hexagonal two-dimensional polymeric frameworks. The polymers are planar in conformation and show flattened frontier levels, which enable electrons to move along the non-conjugated polymeric backbones. The eclipsed face-to-face stack reduces reorganization energy and greatly strengthens electronic coupling, thus enabling band-like electron conduction perpendicular to polymer layers.