Abstract：
Lead chalcogenide colloidal quantum dots are one of the most promising materials to revolutionize the field of short-wavelength infrared optoelectronics due to their bandgap tunability and strong absorption. By self-assembling these quantum dots into ordered superlattices, mobilities approaching those of the bulk counterparts can be achieved while still retaining their original optical properties. The recent literature focused mostly on PbSe-based superlattices, but PbS quantum dots have several advantages, including higher stability. In this work, we demonstrate highly ordered 3D superlattices of PbS quantum dots with tunable thickness up to 200 nm and high coherent ordering, both in-plane and along the thickness. We show that we can successfully exchange the ligands throughout the film without compromising the ordering. The superlattices as the active material of an ion gel-gated field-effect transistor achieve electron mobilities up to 220 cm2 V-1 s-1. To further improve the device performance, we performed a postdeposition passivation with PbI2, which noticeably reduced the subthreshold swing making it reach the Boltzmann limit. We believe this is an important proof of concept showing that it is possible to overcome the problem of high trap densities in quantum dot superlattices enabling their application in optoelectronic devices.
摘要：
硫属铅胶体量子点由于其带隙可调性和强吸收，是最有前途的材料之一，可以彻底改变短波长红外光学领域。通过将这些量子点自组装成有序的超晶格，可以实现接近批量对应物的迁移率，同时仍保留其原始光学特性。最近的文献主要集中在基于PbSe的超晶格上，但是PbS量子点有几个优点，包括更高的稳定性。在这项工作中,我们展示了PbS量子点的高度有序的3D超晶格，具有高达200nm的可调厚度和高相干有序，平面内和沿厚度。我们表明，我们可以成功地在整个薄膜中交换配体，而不会影响排序。作为离子凝胶门控场效应晶体管的活性材料的超晶格可实现高达220cm2V-1s-1的电子迁移率。为了进一步提高器件性能，我们用PbI2进行了沉积后钝化，显着降低了亚阈值摆动，使其达到玻尔兹曼极限。我们认为这是一个重要的概念证明，表明有可能克服量子点超晶格中的高陷阱密度问题，从而使其能够在光电器件中应用。
