Effects of Self-Hybridized Exciton-Polaritons on TMDC Photovoltaics.

Hybrid light-matter states called exciton-polaritons have been explored to improve excitonic photovoltaic (PV) and photodiode efficiency, but the use of closed cavity structures results in efficiency gains over a narrow band, with losses in the short circuit current density under solar illumination. In WX (X = S, Se), the simultaneous large optical constants and strong exciton resonance can result in self-hybridized exciton-polaritons (SHEPs) emerging from the strong coupling of excitons and optical cavity modes formed by WX. We perform thickness dependent device characterization of WS and WSe PVs to show that self-hybridized strong coupling enhances device efficiency on resonance while still enabling broadband absorption, resulting in improved short circuit current density under solar illumination.

Reconfiguration of Amorphous Complex Oxides: A Route to a Broad Range of Assembly Phenomena, Hybrid Materials, and Novel Functionalities.

Reconfiguration of amorphous complex oxides provides a readily controllable source of stress that can be leveraged in nanoscale assembly to access a broad range of 3D geometries and hybrid materials. An amorphous SrTiO layer on a Si:B/Si Ge :B heterostructure is reconfigured at the atomic scale upon heating, exhibiting a change in volume of ≈2% and accompanying biaxial stress. The Si:B/Si Ge :B bilayer is fabricated by molecular beam epitaxy, followed by sputter deposition of SrTiO at room temperature.

Phase Selection and Structure of Low-Defect-Density γ-AlO Created by Epitaxial Crystallization of Amorphous AlO.

A multistep phase sequence following the crystallization of amorphous AlO via solid-phase epitaxy (SPE) points to methods to create low-defect-density thin films of the metastable cubic γ-AlO polymorph. An amorphous AlO thin film on a (0001) α-AlO sapphire substrate initially transforms upon heating to form epitaxial γ-AlO, followed by a transformation to monoclinic θ-AlO, and eventually to α-AlO. Epitaxial γ-AlO layers with low mosaic widths in X-ray rocking curves can be formed via SPE by crystallizing the γ-AlO phase from amorphous AlO and avoiding the microstructural inhomogeneity arising from the spatially inhomogeneous transformation to θ-AlO.