Search

Van der Waals crystals have opened a new and exciting chapter in heterostructure research, removing lattice matching constraints characteristic of epitaxial semiconductors. They provide unprecedented flexibility for heterostructure design. Combining 2D perovskites with other 2D materials, in particular transition metal dichalcogenides (TMDs) has recently emerged as an intriguing way to design hybrid opto- electronic devices. However, the excitation transfer mechanism between the layers (charge or energy transfer) remains to be elucidated. Here we investigate PEA2PbI4/MoSe2 and (BA)2PbI4/MoSe2 heterostructures by combining optical spectroscopy and density functional theory (DFT) calculations. We show that the band alignment facilitates charge transfer. Namely, holes are transferred from the TMD to the 2D perovskite, while the electron transfer is blocked, resulting in the formation of inter-layer excitons. Moreover, we show that the energy transfer mechanism can be turned on by an appropriate alignment of the excitonic states, providing a rule of thumb for the deterministic control of the excitation transfer mechanism in TMD/2D-perovskite heterostructures.

We study an photoluminescence line of a single, self assembled CdTe quantum dot embedded in a field‐effect structure. As a reverse bias is applied the line becomes broader and its intensity is decreased as a result of enhanced escape of the photocreated carriers. We account for the observed effects in a semiclassical model.

We investigate quantum confined Stark shifts for various exciton complexes in a charge tunable CdTe quantum dot. Analysis of the energy positions of exciton transitions allows us to qualitatively address relative strengths of Coulomb interactions between carriers in a dot. We find that electron‐hole attraction is stronger than hole‐hole repulsion, which in turn is stronger than electron‐electron repulsion. These conclusions are strongly supported by the values of measured reduction of excitonic static dipole moment as electrons or holes are controllably added to the dot.