Semiconducting materials are extremely important in the development of electrical and optical devices such as solar cells, optical detectors, and transistors. As devices become smaller and smaller, research has begun to shift from bulk to nanoscale semiconducting materials. There have been many studies conducted on direct-gap semiconducting quantum dots (QDs), including CdSe and PbS, but group IV semiconductors are particularly attractive due to their low toxicity, high abundance, and low cost. Unfortunately, group IV semiconductors have an indirect gap which hampers light-interaction efficiency. To mitigate this, quantum confinement effects and the alloying of tin is applied to transform the indirect energy gap to a direct gap. By varying size and composition direct-gap, tunable Ge1-xSnx QDs that exhibit high absorption and photoluminescent efficiency, and improved electrical properties can be produced. In order to incorporate these enhanced properties into a nano-fabricated device, the QDs must first be processed to produce thin films. A ligand exchange has been conducted, replacing the insulating oleylamine (OLA) with a conducting metal chalcogenide (MCC) as the QD capping ligand allowing for improved charge carrier transport. A comparison of the MCC-capped QDs to the OLA-capped QDs has been performed to probe the effects of the exchange on crystal structure, size, composition, and energy gaps of the QDs. MCC-capped Ge1-xSnx QDs with varying tin compositions were then spin-coated onto a glass substrate producing conducting Ge1-xSnx QD thin films. The tunability and electrical conductivity of these films has been explored. Herein, we will discuss the effects of the ligand exchange, and QD composition on the morphology, crystal structure, thickness, and electrical conductivity of the resulting Ge1-xSnx QD thin films.

Expanding chemical versatility of Ge1–x Snx nanocrystals for the fabrication of thin films with high electrical conductivity and tunable energy gaps

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.