Polymer Semiconductor Charge Transport Mechanisms

Charge transport in polymer semiconductors arises from the movement of charge carriers—electrons and holes—along and between conjugated molecular chains. At the molecular scale, transport occurs via a combination of band-like delocalisation within planar backbone segments and thermally activated hopping between less ordered regions. The extent of π–π stacking, backbone coplanarity and interchain coupling governs the balance between these regimes. Optimising backbone planarity through ring fusion or donor–acceptor unit selection enhances intrachain delocalisation, while side-chain engineering and processing conditions control film morphology, domain formation and defect density. Macroscopically, devices such as organic field-effect transistors (OFETs), organic photovoltaics and chemical sensors leverage these mechanisms to achieve high mobility, balanced ambipolar transport and low threshold voltages. Understanding and controlling the interplay between molecular design, self-assembly and processing remain central to advancing performance and commercial viability of polymer electronic materials.

Research from Nature Portfolio

Recent studies have demonstrated that small-molecule diketopyrrolopyrrole (DPP) derivatives can achieve high field-effect mobilities when judiciously functionalised with siloxane-terminated side chains. Compared to simple branched alkyl chains, the bulky siloxane groups promote more ordered crystallites, leading to enhanced π–π stacking and long-range charge delocalisation. These materials remain soluble in eco-friendly solvents and form uniform films at low annealing temperatures, yielding electron and hole mobilities exceeding 2–3 cm2 V–1 s–1. This work highlights the critical role of side-chain chemistry in tuning thin-film morphology and efficient charge transport in solution-processible semiconductors.

Polymer Semiconductor Charge Transport Mechanisms publication trend

The graph below shows the total number of articles in polymer semiconductor charge transport mechanisms across all publications each year (not limited to Nature Index journals).

Technical terms

π–π stacking: non-covalent overlap of aromatic π‐orbitals between adjacent chains that facilitates interchain charge transfer.

Charge-carrier mobility: the velocity of electrons or holes per unit electric field, indicating semiconductor performance.

Donor–acceptor (D–A) polymer: a conjugated polymer featuring alternating electron-rich (donor) and electron-deficient (acceptor) units to control energy levels and transport pathways.

Coplanarity: the degree to which molecular backbones lie in the same plane, promoting orbital delocalisation and band-like transport.

Side-chain engineering: modification of polymer side groups to influence solubility, packing morphology and charge-transport characteristics.

References

1. Influence of Vinyl Bridging on Transistor Properties of Naphthalenediimide-Based Dual-Acceptor Copolymers. ACS Applied Polymer Materials (2024).
2. Tetramethylammonium Iodide Additive for Enhancing the Charge Carrier Mobilities of Diketopyrrolopyrrole‐Based Conjugated Polymer in Ambipolar Organic Field‐Effect Transistors†. Chinese Journal of Chemistry (2023).
3. Synthesis and Electronic Properties of Diketopyrrolopyrrole-Based Polymers with and without Ring-Fusion. Macromolecules (2021).