Vacancy-Ordered Double Perovskite CsTeI Thin Films for Optoelectronics.

Alternatives to lead- and tin-based perovskites for photovoltaics and optoelectronics are sought that do not suffer from the disadvantages of toxicity and low device efficiency of present-day materials. Here we report a study of the double perovskite CsTeI, which we have synthesized in the thin film form for the first time. Exhaustive trials concluded that spin coating CsI and TeI using an antisolvent method produced uniform films, confirmed as CsTeI by XRD with Rietveld analysis.

Observation of energy transfer at optical frequency to an ultrathin silicon waveguide.

Energy transfer from a submonolayer of rhodamine 6G molecules to a 130 nm thick crystalline silicon (Si) waveguide is investigated. The dependence of the fluorescence lifetime of rhodamine on its distance to the Si waveguide is characterized and modeled successfully by a classical dipole model. The energy transfer process could be regarded as photon tunneling into the Si waveguide via the evanescent waves.

Silicon photosensitisation using molecular layers.

Silicon photosensitisation via energy transfer from molecular dye layers is a promising area of research for excitonic silicon photovoltaics. We present the synthesis and photophysical characterisation of vinyl and allyl terminated Si(111) surfaces decorated with perylene molecules. The functionalised silicon surfaces together with Langmuir-Blodgett (LB) films based on perylene derivatives were studied using a wide range of steady-state and time resolved spectroscopic techniques.

Light harvesting in silicon(111) surfaces using covalently attached protoporphyrin IX dyes.

We report the photosensitization of crystalline silicon via energy transfer using covalently attached protoporphyrin IX (PpIX) derivative molecules at different distances via changing the diol linker to the surface. The diol linker molecule chain length was varied from 2 carbon to 10 carbon lengths in order to change the distance of PpIX to the Si(111) surface between 6 Å and 18 Å. Fluorescence quenching as a function of the PpIX-Si surface distance showed a decrease in the fluorescence lifetime by almost two orders of magnitude at the closest separation.

Photon tunneling into a single-mode planar silicon waveguide.

We demonstrate the direct excitation of a single TE mode in 25 nm thick planar crystalline silicon waveguide by photon tunneling from a layer of fluorescent dye molecules deposited by the Langmuir-Blodgett technique. The observed photon tunneling rate as a function of the dye-silicon separation is well fitted by a theoretical tunneling rate, which is obtained via a novel approach within the framework of quantum mechanics. We suggest that future ultrathin crystalline silicon solar cells can be made efficient by simple light trapping structures consisting of molecules on silicon.

Emission wavelength tuning in rare earth fluoride upconverting nanoparticles decorated with dye-coated titanate nanotubes.

The radiative energy transfer from rare earth fluoride upconverting (UC) Na(x)Li(y)YF(4):Yb(3+),Er(3+) nanoparticles to rhodamine dyes has been systematically studied in colloidal solutions at room temperature. The UC emission bands at 520 and 550 nm have been shifted to the longer-wavelength (ca. 600 nm) region suitable for biomedical applications.