Trap States Ruling Photoconductive Gain in Tissue-Equivalent, Printed Organic X-Ray Detectors

Organic semiconductors are excellent candidates for X-ray detectors that can adapt to new applications, with unique properties including mechanical flexibility and the ability to cover large surfaces. Their chemical composition, primarily carbon and hydrogen, makes them human tissue equivalent in terms of radiation absorption. This is a highly desirable property for a radiation dosimeter to be employed in medical diagnostics and therapy, however a low-Z composition limits the absorption of ionizing radiation. The detection efficiency can be enhanced by considering the photoconductive gain (PG) effect, a significant contributor to the ionizing radiation detection mechanism in this class of materials. In this work, a process of controlled solution deposition by nozzle printing and crystallization of an organic semiconductor thin film is demonstrated whereby a flexible, arrayed thin-film X-ray detector with record X-ray sensitivities among flexible radiation detectors (S = (9.0 +/- 0.4) x 10(7) mu C Gy(-1) cm(-3)) is developed. The excitonic peaks responsible for the activation of the PG effect are investigated and identified using a novel technique called photocurrent spectroscopy optical quenching, and the analysis of the changes in trap states is further demonstrated.

Automated summary

Organic semiconductors are promising materials for X-ray detectors due to their mechanical flexibility and large coverage. The detection efficiency can be enhanced by considering the photoconductive gain effect. This study demonstrates a flexible arrayed thin-film X-ray detector with record X-ray sensitivities using controlled solution deposition and crystallization processes.