Millimeter-scale unipolar transport in high sensitivity organic-inorganic semiconductor X-Ray detectors

Hybrid inorganic-in-organic semiconductors are an attractive class of materials for optoelectronic applications. Traditionally, the thicknesses of organic semiconductors are kept below 1 micron due to poor charge transport in such systems. However, recent work suggests that charge carriers in such organic semiconductors can be transported over centimeter length scales opposing this view. In this work, a unipolar X-ray photoconductor based on a bulk heterojunction architecture, consisting of poly(3-hexylthiophene), a C70 derivative and high atomic number bismuth oxide nanoparticles operating in the 0.1 – 1 mm thickness regime is demonstrated, having a high sensitivity of ~160 µCmGy-1cm-3. The high performance enabled by hole drift lengths approaching a millimeter facilitates a device architecture allowing a high fraction of the incident X-rays to be attenuated. An X-ray imager is demonstrated with sufficient resolution for security applications such as portable baggage screening at border crossings and public events and scalable medical applications

Stable and highly conductive carbon nanotube enhanced PEDOT:PSS as transparent electrode for flexible electronics

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is a popular polymeric material for solution-processed transparent conductive electrodes (TCE), especially on flexible substrates. PEDOT:PSS electrical properties are often improved with a variety of additives. Here, we present an innovative way to furtherly improve the performances of this material by incorporating single walled carbon nanotubes (SWCNTs) into commercially available conductive PEDOT:PSS formulation (Heraeus Clevios™ FE-T). With a load of 0.01 wt% SWCNT, we observed the best trade-off between transparency (91.0% at 550 nm) and sheet resistance (89.1 Ω sq−1). Moreover, we developed a simple and effective lithographic structuring process for these TCEs and we investigated the process effects on its optoelectronic and morphological properties. The developed SWCNT/FE-T electrodes, processed on both glass and flexible PET substrates, were incorporated in organic photodiodes (OPDs), with P3HT:PCBM as active layer. These OPDs show dark current densities, on-off ratios and external quantum efficiencies (EQE) comparable to reference devices comprising indium-tin-oxide (ITO) as TCE. Additionally, this TCE shows superior mechanical and chemical stability, under bending and damp-heat test condition compared to ITO and PEDOT:PSS, respectively