Focus-Induced Photoresponse: a novel way to measure distances with photodetectors.

We present the Focus-Induced Photoresponse (FIP) technique, a novel approach to optical distance measurement. It takes advantage of a universally-observed phenomenon in photodetector devices, an irradiance-dependent responsivity. This means that the output from a sensor is not only dependent on the total flux of incident photons, but also on the size of the area in which they fall. If probe light from an object is cast on the detector through a lens, the sensor response depends on how far in or out of focus the object is. We call this the FIP effect. Here we demonstrate how to use the FIP effect to measure the distance to that object. We show that the FIP technique works with different sensor types and materials, as well as visible and near infrared light. The FIP technique operates on a working principle, which is fundamentally different from all established distance measurement methods and hence offers a way to overcome some of their limitations. FIP enables fast optical distance measurements with a simple single-pixel detector layout and minimal computational power. It allows for measurements that are robust to ambient light even outside the wavelength range accessible with silicon.

Vectorial photoinduced electron transfer in multicomponent film systems of poly(3-hexylthiophene), porphyrin-fullerene dyad, and perylenetetracarboxidiimide.

Multistage electron transfer in a film system consisting of a hole-transporting layer (HTL), donor-acceptor pair (D-A), and an electron-transporting layer (ETL) was studied by photovoltage and flash-photolysis techniques. Poly(3-hexylthiophene) (PHT) was used as the HTL, while a symmetric porphyrin-fullerene dyad (P-F) and perylenetetracarboxidiimide (PTCDI) layers were functioning as the D-A pair and ETL, respectively. The photoexcitation of this three-component film system causes charge separations in the monomolecular P-F film, followed by electron transfer from the PHT polymer film and the fullerene anions to the porphyrin cations and the PTCDI layer, respectively. The final transient state is a charged PHT(+)|P-F|PTCDI(-) system, with significantly increased amplitude and lifetime of the photoelectrical signals compared to previously studied P-F|PTCDI and PHT|P-F systems, due to the its increased charge-separation distance. The study promotes the knowledge on the charge transfer mechanism in multilayered film systems.

Photoinduced electron transfer in thin films of porphyrin-fullerene dyad and perylenetetracarboxidiimide.

Photoinduced intra- and intermolecular electron transfer (ET) in thin films of porphyrin-fullerene dyad (P-F) and perylenetetracarboxidiimide (PTCDI) was studied by means of photoelectrical and spectroscopic methods. Films consisting of smooth 100 mol% layers of P-F and PTCDI were prepared by the Langmuir-Schäfer (LS) technique and thermal evaporation, respectively. The time-resolved Maxwell displacement charge (TRMDC) and laser flash-photolysis methods were utilized to demonstrate photoinduced ET from P-F to PTCDI regardless of which chromophore is photoexcited. Finally, the information about the electron movement in the respective thin films was used to build a layered organic solar cell, whose internal quantum yield (Φ(I)) of collected charges was 13%.