Improvement of the sensitivity of organic polymer-based photodetector fabricated with p-type conjugated polymers for indirect X-ray detection

In this study, an organic polymer-based photodetector was investigated as a candidate for the indirect-type X-ray detector. In order to improve the performance of the photodetector, a conjugated polymer PBDB-T was selected as a p-type material instead of the P3HT that is commonly used as a p-type material to form a bulk-heterojunction active layer with n-type fullerene PC₇₀BM. Absorption spectra of the thin film with 1:1 blending ratio of P3HT: PC₇₀BM and different blending ratios of PBDB-T:PC₇₀BM were measured. PBDB-T:PC₇₀BM-blended film showed higher absorption in the entire visible light range than did P3HT:PC₇₀BM film. The organic photodetectors were fabricated with different blending ratios and spin rates of PBDB-T:PC₇₀BM. The detector fabricated with the PBDB-T:PC₇₀BM = 2:3 blending ratio and spin rate of 1,100 rpm showed the highest collected current density (CCD) and highest sensitivity, which were 434.14 nA/cm² and 3.25 mA/Gy·cm², respectively. This is 152% increase of CCD and 189% of sensitivity over that of the common P3HT:PC₇₀BM photodetector.