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

Efficient intraband hot carrier relaxation in Sn and Pb perovskite semiconductors mediated by strong electron-phonon coupling

The dynamic increase in terahertz photoconductivity resulting from energetic intraband relaxation was used to track the formation of highly mobile charges in thin films of the tin iodide perovskite Cs 1-x Rb x SnI 3 and compared to the lead based Cs 0:05 (FA 0:83 MA 0:17 ) 0:95 Pb(I 0:83 Br 0:17 ) 3 . Energy relaxation times were found to be around 500 fs, comparable to those in GaAs and longer than the ones of the lead-based perovskite (around 300 fs). At low excess energies the efficient intraband relaxation can be understood within the context of the Frohlich electron-phonon interaction. For higher excess energies the photoconductivity rise time lengthens in accordance with carrier injection higher in the bands, or into multiple bands. The findings contribute to the development of design rules for photovoltaic devices capable of extracting hot carriers from perovskite semiconductors