Integration of molecular quantum emitters onto GaN-based LEDs

Scaling LEDs down below the micrometer range enables new strategies to develop optoelectronic devices. By integrating molecular quantum emitters directly onto GaN-based micro- or nano-LEDs, isolated molecules can be efficiently optically pumped and used as single photon sources. Here, we demonstrate the integration of Zinc-Phthalocyanine (ZnPC) molecules onto GaN-based LEDs. ZnPC is well-known for its high chemical and thermal stability. However, improving the emission efficiency in the crystalline phase is still challenging, since fluorescence quenching through excitonic coupling becomes more prominent. To address this issue, we study the emission characteristics of ZnPc thin films, nanoscale molecular clusters and isolated molecular quantum emitters, grown by organic molecular beam epitaxy. In order to reduce the excitonic coupling between the ZnPc molecules, we embedded them into a co-evaporated matrix formed by the alkane tetratetracontane (TTC). Using this approach, we could separate the molecules from each other, which improves the emission intensity. We used a commercial GaN-based LED to demonstrate efficient excitation of the molecules in the ultraviolet spectral range.