Characteristics of an organic photodetector with a conjugated donor and non-fullerene acceptor for indirect X-ray detection

Abstract

In this study, an organic photodetector with a small band-gap donor, PBDB-T, and a non-fullerene acceptor, ITIC, was investigated as the active element in an indirect imaging system using a scintillator of the detector for indirect X-ray imaging. Compared with the common organic photodetector with {a} P3HT:PC70BM active layer, higher conversion efficiencies can be expected, because the proposed detector is advantageous for visible-light absorption and carrier transport. The absorption peak of the PBDB-T:ITIC layer was located at 640 nm and was not well-matched with the emission properties of {a} CsI(Tl) {scintillator}. Therefore, a ZnSe(Te) scintillator with an emission peak at 620 nm was also tested. Compared with the P3HT:PC70BM detector, the ZnSe(Te)-coupled detector with the PBDB-T:ITIC = 1:1 active layer was 191% higher in collected current density (CCD) and 205% higher in sensitivity. The frequency response was measured with a 520 nm green LED. The detector with the PBDB-T:ITIC layer showed the -3 dB cut-off frequency of 31.5 kHz, which was higher than the cut-off frequency of the P3HT:PC70BM detector.