Mitigating Dark Current for High-Performance Near-Infrared Organic Photodiodes via Charge Blocking and Defect Passivation

Abstract

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.

Ultralow dark current in near-infrared perovskite photodiodes by reducing charge injection and interfacial charge generation

“…This is because the sub-bandgap states facilitate the bulk thermal charge generation, which requires electrons in the valence band or occupied intragap states (i.e., deep or shallow traps) to be thermally excited into the conduction band. Although the influence of trap states on J D has been widely observed in inorganic and more recently in OPDs 3 , 40 – 42 , we demonstrate that trap states are unlikely to account for the observed J D in these PPDs. We calculated the dark current density in the radiative limit ( J 0 rad ) and its activation energy ( E a EQE ) from the spectral overlap integral between the black body spectrum at different temperatures and the experimental (sub-bandgap) EQE spectrum (Supplementary Note 2 ).…”

“…Minimizing the dark current density ( J D ) of emerging thin film flexible photodiodes is essential for near-infrared (NIR) sensing and imaging 1 – 3 . Metal halide perovskites are solution processable semiconducting materials that have attracted extensive interest for their remarkable photovoltaic properties 4 , 5 , but are likewise promising candidates for photodiodes.…”

Indocyanine Green-Based Theranostic Nanoplatform for NIR Fluorescence Image-Guided Chemo/Photothermal Therapy of Cervical Cancer

“…23,24 In comparison, the light in the near-infrared (NIR, 760-900 nm) spectral wavelength region has less scattering when traveling through biological samples/tissues. [25][26][27] Thus, NIR light can penetrate and excite deep-tissue regions under the skin. Moreover, NIR fluorescence imaging can offer high contrast and spatial resolution with high sensitivity with limited autofluorescence.…”

Recent Advances in Solution‐Processable Organic Photodetectors and Applications in Flexible Electronics

“…An ultralow J d of ≈0.5 nA cm −2 at −2.0 V and a high D* of over 10 13 Jones at wavelengths up to 940 nm were obtained in NIR OPDs using a cross‐linked PolyTPD electron blocking layer and a mixed C 60 /LiF hole blocking layer. [ 48 ] The cross‐linked PolyTPD layer was found to contribute to an excellent reproducibility and stability of the NIR OPDs. Meanwhile, the trap density and trap‐induced carrier generation in the organic/cathode interface were effectively suppressed by the LiF doping C 60 layer, leading to the ultralow dark current in the NIR OPDs.…”