Enhanced photocurrent in organic photodetectors by the tunneling effect of a hafnium oxide thin film as an electron blocking layer†
To achieve high detectivity of organic photodetectors (OPDs), we investigated hafnium oxide (HfO2) as an electron blocking layer in an attempt to obtain a low leakage current and high photocurrent by the tunneling effect. The prepared devices consisted of indium tin oxide (ITO)/HfO2/(poly(3-hexylthiophene-2,5-diyl)[P3HT]:PC60BM)/Yb/Al. To explore the tunneling effect in a hafnium oxide thin film, we fabricated a thin film using successive ionic layer deposition. The results for hafnium oxide were compared with those for aluminum oxide and poly(3,4-ethylenedioxythiophene)poly(styrenesulfonate) (PEDOT:PSS). We found that hafnium oxide results in a low leakage current and high photocurrent owing to the tunneling effect in the OPDs. The resulting detectivity of 1.76 × 1012 Jones for a film thickness of 5.5 nm and bandwidth of ∼100 kHz is suitable for commercialization.