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

• Published in: ACS applied materials & interfaces 2021-07, Vol.13 (27), p.32022-32030
• Main Authors: Eren, Guncem Ozgun, Sadeghi, Sadra, Bahmani Jalali, Houman, Ritter, Maximilian, Han, Mertcan, Baylam, Isinsu, Melikov, Rustamzhon, Onal, Asim, Oz, Fatma, Sahin, Mehmet, Ow-Yang, Cleva W, Sennaroglu, Alphan, Lechner, Rainer T, Nizamoglu, Sedat
• Format: Article
• Language: English
• Subjects: Functional Nanostructured Materials (including low-D carbon)
• ISSN: 1944-8244; 1944-8252
• DOI: 10.1021/acsami.1c08118

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 type-II 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 ∼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 X-ray 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.