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Solution-Processed Organic Photodetector Using Hafnium Oxide as an Electron Blocking Layer.

Organic photodetector (OPD) performance is affected significantly by leakage current. In this study, to decrease OPD leakage current, we introduced hafnium oxide as an electron blocking material, using a solution fabrication process. We fabricated an OPD consisting of ITO/HfO₂/PCHT:PC60BM/Yb/Al, and measured its J-V characteristics, external quantum efficiency, and transient photocurrents. We found that the thickness of the hafnium oxide layer affected the detectivity of the prepared OPD. In particular, a device having an ultrathin hafnium oxide film (5.5 nm thick) exhibited a high on-off current ratio of up to 2.26 × 105 at -1 V, which is two times higher than that of a device having a PEDOT:PSS electron blocking layer.