Thin-film
organic near-infrared (NIR) photodiodes can be essential
building blocks in the rapidly emerging fields including the internet
of things and wearable electronics. However, the demonstration of
NIR organic photodiodes with not only high responsivity but also low
dark current density that is comparable to that of inorganic photodiodes,
for example, below 1 nA cm–2 for silicon photodiodes,
remains a challenge. In this work, we have demonstrated non-fullerene
acceptor-based NIR photodiodes with an ultralow dark current density
of 0.2 nA cm–2 at −2 V by innovating on charge
transport layers to mitigate the reverse charge injection and interfacial
defect-induced current generation. The same device also shows a high
external quantum efficiency approaching 70% at 850 nm and a specific
detectivity of over 1013 Jones at wavelengths up to 940
nm. Furthermore, the versatility of our approach for mitigating dark
current is demonstrated using a NIR photodetector utilizing different
non-fullerene systems. Finally, the practical application of NIR organic
photodiodes is demonstrated with an image sensor integrated on a silicon
CMOS readout. This work provides new insight into the device stack
design of low-dark current NIR organic photodiodes for weak light
detection.
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