Strain-durable dark current in near-infrared organic photodetectors for skin-conformal photoplethysmographic sensors

Eun, Hyeong Ju; Lee, Hanbee; Shim, Yeongseok; Seo, Gyeong Uk; Lee, Ah Young; Heo, Junseok; Park, Sung-Jun; Kim, Jong H.

doi:10.1016/j.isci.2022.104194

Cited by 16 publications

(23 citation statements)

References 37 publications

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“…To our knowledge, for any given D-A combination, these diodes have J d and i n values on par or better than the corresponding D-A devices in the literature. [23,24,28,[34][35][36] We attribute this to careful device optimization together with the use of an ECL and a relatively thick BHJ layer of 280 ± 10 nm. The ultralow J d in these diodes provides a thus far unparalleled opportunity to investigate its intrinsic origin and explore possible mechanisms to further reduce the J d in OPDs.…”

Section: Thermally Activated Dark Current In Bhj Photodiodesmentioning

confidence: 99%

Identification of the Origin of Ultralow Dark Currents in Organic Photodiodes

Bin

Gorkom

et al. 2022

Advanced Materials

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Organic bulk heterojunction photodiodes (OPDs) attract attention for sensing and imaging. Their detectivity is typically limited by a substantial reverse bias dark current density (Jd). Recently, using thermal admittance or spectral photocurrent measurements, Jd has been attributed to thermal charge generation mediated by mid‐gap states. Here, the temperature dependence of Jd in state‐of‐the‐art OPDs is reported with Jd down to 10−9 mA cm−2 at −0.5 V bias. For a variety of donor‐acceptor bulk‐heterojunction blends it is found that the thermal activation energy of Jd is lower than the effective bandgap of the blends, by ca. 0.3 to 0.5 eV, but higher than expected for mid‐gap states. Ultra‐sensitive sub‐bandgap photocurrent spectroscopy reveals that the minimum photon energy for optical charge generation in OPDs correlates with the dark current thermal activation energy. The dark current in OPDs is attributed to thermal charge generation at the donor‐acceptor interface mediated by intra‐gap states near the band edges.

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Section: Thermally Activated Dark Current In Bhj Photodiodesmentioning

confidence: 99%

Identification of the Origin of Ultralow Dark Currents in Organic Photodiodes

Bin

Gorkom

et al. 2022

Advanced Materials

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“…To obtain more conformable on-skin PPG systems for wearable applications, OPDs have been fabricated on an ultrathin flexible substrate and integrated with light sources of either LEDs or organic LEDs (OLEDs), showing their capability of detecting theheart rate, blood oxygen content, and blood pressure for medical diagnostics [135][136][137]. Yokota et al fabricated an ultra-flexible reflective pulse oximeter based on an OPD with a structure of ITO/P3HT:PCBM/ MoO x /Au on a PI planarized perylene substrate [138].…”

Section: Wearable Medical Diagnosticsmentioning

confidence: 99%

Organic photodiodes: device engineering and applications

Shan

Hou

Yin

et al. 2022

Front. Optoelectron.

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Organic photodiodes (OPDs) have shown great promise for potential applications in optical imaging, sensing, and communication due to their wide-range tunable photoelectrical properties, low-temperature facile processes, and excellent mechanical flexibility. Extensive research work has been carried out on exploring materials, device structures, physical mechanisms, and processing approaches to improve the performance of OPDs to the level of their inorganic counterparts. In addition, various system prototypes have been built based on the exhibited and attractive features of OPDs. It is vital to link the device optimal design and engineering to the system requirements and examine the existing deficiencies of OPDs towards practical applications, so this review starts from discussions on the required key performance metrics for different envisioned applications. Then the fundamentals of the OPD device structures and operation mechanisms are briefly introduced, and the latest development of OPDs for improving the key performance merits is reviewed. Finally, the trials of OPDs for various applications including wearable medical diagnostics, optical imagers, spectrometers, and light communications are reviewed, and both the promises and challenges are revealed. Graphical Abstract

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“…Notably, these values are similar to those of the recently reported OPDs (Table S4). − However, the R and D * of the flexible OPDs fabricated with the ZnO-NP and ZnO-NP:KBr ETLs/HBLs were gradually decreased after bending 500 and 1000 times at r = 4.0 mm, whereas the ZnO-NP:DFPBr-6 device produced almost identical R and D * regardless of bending cycles (Figure d). The R values of the ZnO-NP and ZnO-NP:KBr devices were decreased to 0.06 and 0.02 A/W corresponding to 85 and 95% reductions, respectively, after bending 1000 times at r = 4.0 mm (Table S3).…”

Section: Resultsmentioning

confidence: 97%

Flexible Organic Photodetectors with Mechanically Robust Zinc Oxide Nanoparticle Thin Films

Byeon

Kim

Hwang

et al. 2023

ACS Appl. Mater. Interfaces

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Zinc oxide nanoparticle (ZnO-NP) thin films have been intensively used as electron transport layers (ETLs) in organic optoelectronic devices, but their moderate mechanical flexibility hinders their application to flexible electronic devices. This study reveals that the multivalent interaction between ZnO-NPs and multicharged conjugated electrolytes, such as diphenylfluorene pyridinium bromide derivative (DFPBr-6), can significantly improve the mechanical flexibility of ZnO-NP thin films. Intermixing ZnO-NPs and DFPBr-6 facilitates the coordination between bromide anions (from the DFPBr-6) and zinc cations on ZnO-NP surfaces, forming Zn 2+ −Br − bonds. Different from a conventional electrolyte (e.g., KBr), DFPBr-6 with six pyridinium ionic side chains holds the Br − -chelated ZnO-NPs adjacent to DFP + through Zn 2+ −Br − −N + bonds. Consequently, ZnO-NP:DFPBr-6 thin films exhibit improved mechanical flexibility with a critical bending radius as low as 1.5 mm under tensile bending conditions. Flexible organic photodetectors with ZnO-NP:DFPBr-6 thin films as ETLs demonstrate reliable device performances with high R (0.34 A/W) and D* (3.03 × 10 12 Jones) even after 1000 times repetitive bending at a bending radius of 4.0 mm, whereas devices with ZnO-NP and ZnO-NP:KBr ETLs yield >85% reduction in R and D* under the same bending condition.

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Strain-durable dark current in near-infrared organic photodetectors for skin-conformal photoplethysmographic sensors

Cited by 16 publications

References 37 publications

Identification of the Origin of Ultralow Dark Currents in Organic Photodiodes

Identification of the Origin of Ultralow Dark Currents in Organic Photodiodes

Organic photodiodes: device engineering and applications

Flexible Organic Photodetectors with Mechanically Robust Zinc Oxide Nanoparticle Thin Films

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