A mixed-dimensional 1D Se–2D InSe van der Waals heterojunction for high responsivity self-powered photodetectors

Mixed-dimension van der Waals (vdW) p–n heterojunction photodiodes have inspired worldwide efforts to combine the excellent properties of 2D materials and traditional semiconductors without consideration of lattice mismatch. However, owing to the scarcity of intrinsic p-type semiconductors and insufficient optical absorption of the few layer 2D materials, a high performance photovoltaic device based on a vdW heterojunction is still lacking. Here, a novel mixed-dimension vdW heterojunction consisting of 1D p-type Se nanotubes and a 2D flexible n-type InSe nanosheet is proposed by a facile method, and the device shows excellent photovoltaic characteristics. Due to the superior properties of the hybrid p–n junction, the mix-dimensional van der Waals heterojunction exhibited high on/off ratios (103) at a relatively weak light intensity of 3 mW cm−2. And a broadband self-powered photodetector ranging from the UV to visible region is achieved. The highest responsivity of the device could reach up to 110 mA W−1 without an external energy supply. This value is comparable to that of the pristine Se device at 5 V and InSe device at 0.1 V, respectively. Furthermore, the response speed is enhanced by one order of magnitude over the single Se or InSe device even at a bias voltage. This work paves a new way for the further development of high performance, low cost, and energy-efficient photodetectors by using mixed-dimensional vdW heterostructures.