Low dark current inverted organic photodetectors employing MoOx:Al cathode interlayer

• A cathode interlayer (MoOx:Al) has been introduced to inverted organic photodetectors.
• The interlayer exhibited reduction in device dark currents to 0.25–5.6 nA/cm2 at 3 V.
• Accordingly, high detectivity ∼8.95 × 1012 Jones at 3 V was achieved.
• Possible origins of reduced dark currents were further described.

We report low dark current small molecule organic photodetectors (OPDs) with an inverted geometry for image sensor applications. Adopting a very thin MoOx:Al cathode interlayer (CIL) in the inverted OPD with a reflective top electrode results in a remarkably low dark current density (Jd) of 5.6 nA/cm2 at reverse bias of 3 V, while maintaining high external quantum efficiency (EQE) of 56.1% at visible wavelengths. The effectiveness of the CIL on the diode performance has been further identified by application to inverted OPDs with a semi-transparent top electrode, leading to a significantly low Jd of 0.25 nA/cm2, moderately high EQE540 nm of 25.8%, and subsequently high detectivity of 8.95 × 1012 Jones at reverse bias of 3 V. Possible origins of reduced dark currents in the OPD by using the MoOx:Al CIL are further described in terms of the change of interfacial energy barrier and surface morphology.

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