Investigation of X-Ray-induced effects in hybrid and organic semiconductors by UV–Vis photocurrent spectroscopy

Investigating how ionizing radiation interacts with condensed matter is essential for developing next‑generation radiation sensors and radiation‑hard electronics. Traditional ex‑situ degradation studies cannot capture real‑time transient electronic processes during exposure, while existing in‑situ approaches are mostly limited to fixed‑wavelength probes. This thesis addresses this gap through the design and implementation of a compact apparatus enabling continuous UV‑Vis photocurrent spectroscopy under simultaneous steady‑state X‑ray irradiation. The project also involved upgrading a standard UV‑Vis photocurrent spectroscopy setup, validated on a BA2PbI4 thin‑film photoconductor. From its photocurrent spectrum, the responsivity profile was derived, and the energy gap and binding energy were extracted using a truncated 3D Elliott fit. This system was then used to acquire photocurrent spectra and responsivity profiles for all other investigated materials, providing a benchmark for co‑irradiation sweeps in the new setup. Under X‑rays, the low‑dimensional PEA2PbBr4 thin film showed notable radiation hardness and transparency, with no electrical changes. Conversely, the PEA2PbBr4 single crystal exhibited a strong enhancement and broadening of its excitonic features. For the 3D vertical MAPbBr3 single crystal, simultaneous X‑ray exposure induced a marked increase in the excitonic peak accompanied by complete quenching of the continuum photocurrent, likely driven by enhanced exciton‑phonon coupling due to radiation‑induced bromine vacancies. Finally, the organic TIPS‑PEN thin‑film photoconductor displayed a fully reversible enhancement of its vibronic peaks within a 17‑hour recovery window, along with a reproducible blueshift of the energy gap extracted from modified Tauc plots. The absence of continuum quenching in both TIPS‑PEN and the PEA2PbBr4 single crystal suggests that X‑ray‑induced defects in these systems do not act as dominant recombination centers for excitons.