Two-dimensional hole gas in organic semiconductors

A highly conductive metallic gas that is quantum mechanically confined at a solid-state interface an ideal platform to explore nontrivial electronic states are otherwise inaccessible in bulk materials. Although two-dimensional electron (2DEG) has been realized conventional semiconductor interfaces, examples of hole (2DHG), which the counter analogue 2DEG, still limited. Here, we report observation 2DHG solution-processed organic semiconductors conjunction with electric double-layer using ionic liquids. molecularly flat single crystal high mobility serves as defect-free facilitates confinement high-density holes. Remarkably low sheet resistance 6 k$\Omega$ and density 10$^{14}$ cm$^{-2}$ result metal-insulator transition ambient pressure. The measured degenerated holes provide broad opportunity tailor low-dimensional engineered heterointerfaces.