Cadmium-Free and Efficient Type-II InP/ZnO/ZnS Quantum Dots and Their Application for LEDs


Eren G. O. , Sadeghi S., Jalali H. B. , Ritter M., Han M., Baylam I., ...More

ACS APPLIED MATERIALS & INTERFACES, vol.13, no.27, pp.32022-32030, 2021 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 13 Issue: 27
  • Publication Date: 2021
  • Doi Number: 10.1021/acsami.1c08118
  • Title of Journal : ACS APPLIED MATERIALS & INTERFACES
  • Page Numbers: pp.32022-32030

Abstract

It is a generally accepted perspective that type-II nanocrystal quantum dots (QDs) have low quantum yield due to the separation of the electron and hole wavefunctions. Recently, high quantum yield levels were reported for cadmium-based typeII QDs. Hence, the quest for finding non-toxic and efficient type-II QDs is continuing. Herein, we demonstrate environmentally benign type-II InP/ZnO/ZnS core/shell/shell QDs that reach a high quantum yield of similar to 91%. For this, ZnO layer was grown on core InP QDs by thermal decomposition, which was followed by a ZnS layer via successive ionic layer adsorption. The small-angle Xray scattering shows that spherical InP core and InP/ZnO core/ shell QDs turn into elliptical particles with the growth of the ZnS shell. To conserve the quantum efficiency of QDs in device architectures, InP/ZnO/ZnS QDs were integrated in the liquid state on blue light-emitting diodes (LEDs) as down-converters that led to an external quantum efficiency of 9.4% and a power conversion efficiency of 6.8%, respectively, which is the most efficient QD-LED using type-II QDs. This study pointed out that cadmium-free type-II QDs can reach high efficiency levels, which can stimulate novel forms of devices and nanomaterials for bioimaging, display, and lighting.