Morten Schmidt

A hybrid CMOS-imager with a solution-processable polymer as photoactive layer

The solution-processability of organic photodetectors allows a straightforward combination with other materials, including inorganic ones, without increasing cost and process complexity significantly compared with conventional crystalline semiconductors. Although the optoelectronic performance of these organic devices does not outmatch their inorganic counterparts, there are certain applications exploiting the benefit of the solution-processability. Here we demonstrate that the small pixel fill factor of present complementary metal oxide semiconductor-imagers, decreasing the light sensitivity, can be increased up to 100% by replacing silicon photodiodes with an organic photoactive layer deposited with a simple low-cost spray-coating process. By performing a full optoelectronic characterization on this first solution-processable hybrid complementary metal oxide semiconductor-imager, including the first reported observation of different noise types in organic photodiodes, we demonstrate the suitability of this novel device for imaging. Furthermore, by integrating monolithically different organic materials to the chip, we show the cost-effective portability of the hybrid concept to different wavelength regions.

Spray coated indium-tin-oxide-free organic photodiodes with PEDOT:PSS anodes

In this paper we report on Indium Tin Oxide (ITO)-free spray coated organic photodiodes with an active layer consisting of a poly(3-hexylthiophen) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) blend and patterned poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) electrodes. External quantum efficiency and current voltage characteristics under illuminated and dark conditions as well as cut-off frequencies for devices with varying active and hole conducting layer thicknesses were measured in order to characterize the fabricated devices. 60% quantum efficiency as well as nearly four orders of magnitude on-off ratios have been achieved. Those values are comparable with standard ITO devices.

Large Area Nano-transfer Printing of Sub-50-nm Metal Nanostructures Using Low-cost Semi-flexible Hybrid Templates

In this work, we present a method for printing metal micro- and nanopatterns down to sub-50-nm feature sizes using replicated, defect-tolerant stamps made out of OrmoStamp®; material. The relevant parameters for a successful transfer over large areas were investigated and yields above 99 % have been achieved. Comparing our results to conventional nano-transfer printing using PDMS stamps, we find that the more rigid hybrid polymer used here prevents unintended transfer from interspaces between structures of large distance due to roof collapse and deformation of nano-sized structures due to lateral collapse. Yet, our stamps are flexible enough to ensure intimate contact with the underlying substrate over large areas even in the presence of defect particles. Additionally, the presented patterning technique is resist-, solvent-, and chemical-free and is therefore ideally suited for applications in organic nanoelectronics where standard nanostructuring methods can harm or destroy the organic material.

Nanopatterning of P3HT:PCBM for organic solar cell realization

Organic solar cells (OSC) are becoming an important alternative to standard inorganic ones since they have many intrinsic advantage, such as light weight, flexibility, and low fabrication costs. The use of plasmonic backcontact grating with nanometric pitch can enhance the absorption in the active layer of organic solar cell and consequently increase the power conversion efficiency. We realized P3HT:PCBM films with a nanopatterned architecture. With transmission measurements and with the aid of simulations we demonstrate the increase of the absorption in the P3HT:PCBM film. This approach can be used to increase the efficiency in OSC. 20 working solar cells with flat and structured architecture were realized and the average efficiency of structured cells was 13.7 % higher than that of flat cells.