Alexander Eychmüller

Surface-state emission enhancement in white-luminophor CdS nanocrystals using localized plasmon coupling

To make surface-state emission stronger than band-edge emission for the first time, we proposed and demonstrated plasmon coupling of the surface-state emission from the traps in these CdS nano-luminophors using localized plasmons.

Polymer-facilitated low temperature fusing of spray-coated silver nanowire networks as transparent top and bottom electrodes in small molecule organic photovoltaics (Presentation Recording)

Networks of silver nanowires (AgNWs) are promising candidates for transparent conducting electrodes in organic photovoltaics (OPV), as they achieve similar performance as the commonly used indium tin oxide (ITO) at lower cost and increased flexibility. The initial sheet resistance (Rs) of AgNW electrodes typically needs to be reduced by a post-annealing step (90 min@200 °C), being detrimental for processing on polymeric substrates. We present novel low temperature-based methods to integrate AgNWs in organic small molecule-based photovoltaics, either as transparent and highly conductive bottom-electrode or, for the first time, as spray-coated AgNW top-electrode. The bottom-electrodes are prepared by organic matrix assisted low-temperature fusing. Here, selected polymers are coated below the AgNWs to increase the interaction between NWs and substrate. In comparison to networks without these polymeric sublayers, the Rs is reduced by two orders of magnitude. AgNW top-electrodes are realized by dispersing modified high-quality AgNWs in inert solvents, which do not damage small molecule layers. Accordingly, our AgNW dispersion can be spray-coated onto all kind of OPV devices. Both bottom- and top-electrodes show a Rs of <11 Ω/ at >87 % transparency directly after spray-coating at very low substrate temperatures of <80 °C. We also demonstrate the implementation of our AgNW electrodes in organic solar cells. The corresponding devices show almost identical performance compared to organic solar cells exploiting ITO as bottom or thermally evaporated thin-metal as top-electrode.

White CdS Nanoluminophore based Tunable Hybrid Light Emitting Diodes

The study aims to fabricate and demonstrate hybrid white light emitting diodes that integrate white emitting CdS nanoluminophores with high light quality. Results show that the white light properties of these hybrid WLED (including (x,y) chromaticity coordinates, color temperature, and color rendering index (Ra)) are conveniently tuned as desired across the white region by controlling the number of these surface state emitting nanoluminophores hybridized on the n-UV LED platform. In this tuning process, with the increasing number of the hybridized surface state emitting nanocrystals, it is observed that (x,y) and Ra increase while Tc decreases.