Fabrication and characterisation of hybrid photodiodes based on PCPDTBT–ZnO active layers

• Wide photoresponse from UV to the NIR is achieved.
• Device exhibits low dark current and high rectification ratio for a hybrid device.
• Responsivity is measured and shown to be linear for incident power >0.04 W/cm2.
• Improved lifetime observed with PCPDTBT active layer, when compared to P3HT-based devices.

We report the fabrication and characterisation of an organic–inorganic hybrid photodiode (HPD) based on PCPDTBT and Zinc Oxide (ZnO) photoactive layers. The main benefit of using these materials is that multi spectral light sensing from the UV through to the Near Infrared is achieved, encompassing wavelengths ∼350–870 nm. To our knowledge, this is one of the widest range responses reported for an inorganic–organic hybrid photodiode. The evaluation of the technology shows the devices exhibit one of the lowest levels of dark currents reported for a HPD, but some limitations exist due to a low on–off ratio and non-linearity of the responsivity at low incident power. The stability of devices made with PCPDTBT:ZnO active layers is compared to more commonly reported P3HT:ZnO devices in dark and it is shown that using PCPDTBT substantially improves lifetime.

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