Organic light-emitting diodes (OLEDs) based on thermally activated delayed fluorescence (TADF) show increased efficiencies due to efficient upconversion of nonemissive triplet states to emissive singlet states via reverse intersystem crossing (RISC). To assess the influence of the characteristic efficiency-enhancing RISC process as well as possible efficiency-limiting effects on operational OLEDs, we performed temperaturedependent measurements of transient electroluminescence (trEL). With kinetic modeling, we quantify and separate the impact of different temperature-dependent depopulation processes and contributions to EL in the established donor:acceptor model system m-MTDATA:3TPYMB. The underlying rate equations adapted for EL measurements on TADF systems include radiative and nonradiative firstand second-order effects. In this way, we are able to evaluate the nonradiative recombination and annihilation processes with respect to their efficiency-limiting effects on these OLEDs. On the one hand, we evaluate the depopulation of intermolecular exciplex triplet states via nonradiative direct triplet decay, RISC, and triplet−triplet annihilation (TTA). On the other hand, we determine the contribution to EL from the formation of singlet exciplex states via polarons, RISC, and TTA. Our results show that TTA accounts for a significant part of triplet depopulation and contributes to EL while limiting the overall device quantum efficiency.

The introduction of topological physics into the field of photonics has led to the development of photonic devices endowed with robustness against structural disorder. While a range of platforms have been successfully implemented demonstrating topological protection of light in the classical domain, the implementation of quantum light sources in photonic devices harnessing topologically nontrivial resonances is largely unexplored. Here, we demonstrate a single photon source based on a single semiconductor quantum dot coupled to a topologically nontrivial Su−Schrieffer−Heeger (SSH) cavity mode. We provide an in-depth study of Purcell enhancement for this topological quantum light source and demonstrate its emission of nonclassical light on demand. Our approach is a promising step toward the application of topological cavities in quantum photonics.

Quantum memories can substantially increase the efficiency of long-distance communications by synchronizing entanglement swapping operations in quantum repeater nodes. To build a quantum memory, electromagnetically induced transparency (EIT) in atomic vapors can be exploited to coherently store light pulses even at room temperatures. As a quantum source of light, semiconductor quantum dots (QD) offer bright on-demand single photons with high purity.4 Interfacing QDs with atomic vapors has been shown by “slow light” but a quantum memory for QDs is yet to be demonstrated. In this work, we develop an EIT quantum memory hosted in warm cesium vapor. Storage of faint coherent light pulses on the single photon level shows high storage efficiency. A measured bandwidth in the order of 200 MHz makes the memory compatible with the Fourier-limited emission of QDs embedded in micropillar cavities. We show the first attempts to interface the emission from a QD-micropillar with our quantum memory by finetuning the emission wavelength of the emitters to one of the hyperfine transitions in Cs, where the EIT memory takes place. This work sets the base for a hybrid quantum memory based on atomic ensembles for an on-demand semiconductor single-photon source.

The aim of this work is to use different online comparison calculators in order to compare the results and to work out limitations and potentials for improvement. The research hypothesis is that due to uniform initial data of the case study, the different calculators provide approximately the same results. To investigate this hypothesis, four steps are carried out: first research and categorization of online calculators; second creating a case study and scenarios; third application of online calculators and fourth comparing the results of the calculations, also with the benchmark calculator DIPO-tool, for a critical evaluation. Generally, one can say that only a small number of the reviewed calculators can provide a functionality that is necessary for a professional and proper comparison of economic efficiency and sustainability. For the economic comparison, one can state, that in some cases, the calculation results deviate strongly from each other, contrary to the formulated hypothesis. When considering sustainability, it becomes very clear that tankto-wheel and well-to-wheel considerations fall far short of the mark and must be supplemented by a holistic approach that includes the manufacturing phase and the after-use phase (recovery and recycling).