Two different position sensitive devices for large-area detection of light points and objects are presented. The core of the
system consists of a luminescent foil, where impinging laser light is absorbed and the fluorescence light is coupled out
via attached silicon photodiodes. Due to a direct relation between the signal amplitude and the distance to the
photodiodes, this detector can be used for pinpointing laser spots over large areas. When fixing small stripes of the
detector inside a rectangular frame, the foil can be used for object tracing over large-areas as well.
In this study, we have investigated the possibility to realize different types of stacked, serially connected organic solar cells. First of all, we combined solution processed MDMO-PPV:PCBM or P3HT:PCBM and evaporated ZnPc-C60 bulk-heterojunction solar cells to achieved tandem cells exploiting the complementary absorption spectra of each single cells. Such devices exhibit open circuit voltages of 1V with a short-circuit current of approximately 5mA/cm2 and a fill factor of 0.35 under simulated AM1.5 illumination. In the case of stacked, series connected cells with all active layers processed from solution, we observed a significant increase of the open circuit voltage in comparison with the single junction cells: Device fabricated from two bilayers comprising MDMO-PPV and PCBM as photoactive materials exhibit 1.28V open circuit voltage, 1.1mA/cm2 short circuit current and a fill factor of 0.45 under simulated AM1.5 illumination.
We compare different structures of organic solar cells based on zinc phthalocyanine (ZnPc) and fullerene derivatives as electron donor and acceptor materials, respectively. Bilayer devices are fabricated and characterized by current-voltage and spectrally resolved photocurrent measurements. In a novel approach, the ZnPc was combined with soluble fullerene derivatives. With a pyrrolidinofullerene bearing chelating pyrridyl-groups we observed a complexation between donor and acceptor molecules. Due to a favorable structuring of the donor-acceptor interface this leads to a significant enhancement of the solar cell performance compared to similar devices where no complexation takes place. Coevaporated bulk heterojunction mixed-layers are introduced between the pristine layers. In these optimized structures short circuit currents up to 13 mA/cm2 are observed. We investigate the voltage dependence of the spectrally resolved photocurrent of ZnPc / Buckminsterfullerene bilayer solar cells and interpret the results in terms of the Gartner model.
Photo-induced phenomena were investigated in photoresposive organic field-effect transistors (photOFETs) based on conjugated polymer/fullerene solid-state mixtures as active semiconductor layer and divinyltetramethyldisiloxane-bis(benzocyclobutene) (BCB) as gate dielectrics. The devices were characterized both in under dark showing n-type transistor behaviour with linear and saturated mobility of 1.7 x 10-3 cm2/Vs and 2.7 x 10-2 cm2/Vs respectively, and under white light illumination condition, where large shifts in the threshold voltage in the transfer characteristics were obtained. A typical phototransistor behaviour in a wide range of illumination intensities are observed in these devices.